Okay, since I have some time on my hands this week, I thought I'd post something productive. And really, really long. 
There have been a bunch of threads here at TB recently about how to learn a song "by ear," and some of us have pretty much been saying, "Just &$#%! do it." Well, that's easy to say, but if you know nothing about music, that's a pretty tall order (it's even tougher if you're lazy and stupid, but that's a rant for another day
). So, I figured I'd share how I do it. I posted something similar a coupla years ago too, but that was a few server changes ago, so it's long gone (I think). Please keep in mind that there are lots of guys on here who can do it better than I, and will probably poke holes in my approach. I don't have a problem with that, as long as their criticism is constructive. And please keep in mind this is for basic, off-the-radio rock/pop tunes - not jazz. That requires a different set of rules, not to mention a shorter strap. 
First of all, learning a song by "ear" isn't learning a song by ear at all - it's learning by BRAIN. Your ear can't analyze anything unless your brain is engaged. And even guys who don't have formal theory training are STILL applying what they've learned informally through experience. But if you know a even a little about how songs are put together, it makes your life a lot easier. So, there will be some basic theory involved in this. Please do not be frightened - it DOES NOT STIFLE CREATIVITY IN ANY WAY. Don't buy into that crap. You will still have a 48" vertical leap and it will not cause your tattoos to fade. This approach presumes you know at least the BASICS of music theory - key sigs, time sigs, major vs. minor, etc. If you don't, come back when you do, okay? No one is going to spoon feed you.
Anyway, here goes:
TUNE YOUR DAMN BASS: Okay, you vets are laughing, but I learned a long time ago that NOTHING is too basic. The reason for this step should be obvious. If it's not, SELL YOUR BASS RIGHT NOW. Please. [NOTE: Some artists, for a variety of reasons may be tuned slightly off from A440. If so, tune to the recording while you're learning the tune.]
Figure out the key and time signatures: Okay, I already lost some of you. Sorry, but if you can't figure out the key and time sigs you are doomed to a lifetime of hunting and pecking on the fingerboard looking for the right notes. The time sig is 4/4 for most rock/pop tunes, but it can be anything from 5/4 to 6/8 to 37/64 if it's Rush
. But if you know what a time signature IS, figuring it out is usually a no-brainer. The key sig can be a little trickier. The usual shortcut is to listen to the first and last notes of the song, which works probably 80% of the time. However, the key may shift (modulate) somewhere in the middle of the tune, and may or may not return to the original key. You also need to know whether the tune is major or minor. After you've been at it for a while, your ear (brain) will tell you. If you're having trouble figuring it out, play some major/minor thirds and see which fits. If it's minor, determine the relative major to at least get a starting key signature.
IMPORTANT NOTE: If the starting note is Eb, and the tune is less than ten years old, it's likely the instruments are tuned down a half step (Eb,Ab,Db,Gb). If it's in D, there's a good chance it's in "Drop D," which means the E string ONLY is tuned down a full step (D,A,D,G). Personally, when I played a four I would tune 'em all down in drop D, because I think drop D is stupid and didn't like having to think about where the notes where, although that does make the fingering trickier. The point of drop D is so the guitars can do their stupid "power chord" root/fifth thing (D/A/D). Creed especially is guilty of this. Beware.
Figure out the chord progession: [Note: If we were talking about jazz, this step would be before figuring out the key signature. But we ain't, so it isn't] Figuring out a tune note by note is doing it the hard way. Figure the chord movement out FIRST, THEN go back and fill in the connecting notes. When you write a song, that's how you do it, right? You have a chord structure and you create a line that fits that structure. So learn the tune the same way. If you are having a hard time hearing the bass line, listen to the rhythm guitar changes. It also helps to know simple chord progressions: I-V-I, I-IV-V-I, I-vi-ii-V-I, etcetera. That is, if it starts on I, your next chord is likely to be V, if you're on V, your next chord is likely to be I. After a while, you'll be able to hear the intervals yourself. But take the time to figure out the overall chord progression and WRITE IT DOWN. And if you just write the changes (I-IV-V-I) instead of the root notes (C-F-G-C), you can refer to it to play the tune IN ANY KEY (Holy versatility, Batman!). I'm not going to get into things like alternate key centers (V's suddenly acting as I's, etc.), but realize they exist, and can make your life hell. Also, in a lot of blues-bases stuff, EVERY chord is a dominant seven (I7-IV7-V7-I7, etc.), which technically means nothing really resolves. This may bug purists, but try not to let it ruin your life. Just play flat 7's.
Figure out where the guy is playing on the neck: I can't overemphasize this point. If you can figure out where the guy is playing on the neck, it'll give you a much better idea of what your note choices are. Bass players are as lazy as anyone else (no!), and don't generally make giant intervalic leaps if they don't have to. This is the biggest problem with tab, IMO. You see how someone tabbed something and you KNOW the guy who is playing on the CD isn't doing anything like that - he'd need three hands. YOU SHOULDN'T BE LEAPING ALL OVER THE NECK. Would you write a tune like that? C'mon. And if you can figure out HOW he is playing, you'll have insight into WHAT he is playing. Listen to the tone. Is it growly? Then he's down on the lower frets. Is it round and tubey? Then it's further up the neck. Is he using open strings? Is he playing a five? Is he using a pick? All of this stuff will give you a clue. And if you 'scribe a lot of stuff by the same guy, you'll start to learn his habits and cliches as well. Even guys like Geddy Lee and Les Claypool (okay, ESPECIALLY Les) end up playing the same crap over and over. They're human too.
Connect the chords: Now it's time to connect the chords. There are lots of ways to this, and this is where there is likely to be the most debate. But what you want to figure out is how the other guy did it, regardless. If you want to learn the tune note for note, then this is where the dirty work is. But if you know the key and the chord progression, your job is made MUCH easier. Start with chord tones within the key (1,3,5), then other tones within the key (2,4,6,7), and if none of those are working, go with chromatic tones (notes outside of the key). If it sounds particularly "jazzy," there are probably a few notes outside of the key sig (esp flat fives/sevens). If it's a simple blues-based tune or something where the bass line isn't particulary prominent (or if it just sucks and you think you can do better), you can get away with creating your own line based on the chord progression. Again, lots of ways to do this. I tend to think modally (see other threads on modes), but to each his own. Just remember that if you work too far outside of the key sig you're gonna end up with "Donna Lee," and God Knows We Don't Want That.
This is also where being able to hear intervals can be a huge help. On complicated tunes sometimes you're better off memorizing the line to the point where you can sing it in your head (or better yet, out loud), and then figuring it out. That saves some wear and tear on your CD player too. Which brings us to...
DON'T GIVE UP!: This is probably the most important advice of all, and has been given a zillion ****ing times here and no one seems to listen. This all takes time. You won't be able to do it all overnight. If you want to be any good at this, it can take years. But if you don't buckle down and DO IT YOURSELF, you will never, EVER be able to do it. And asking people to do it for you is not only lazy and rude, but is just hurting your own progress as a musician. THERE IS NO EASY WAY. So quit asking.
Anyway, I think that's about it. Again, this is all very generalized, and makes some fairly broad assumptions, and doesn't deal with avoid notes, alternate key centers, modes, body piercings, etcetera. But it should at least give you a methodic approach. I certainly invite others to clarify or add their tips. But let's try to keep it constructive, and if possible directed more at the rock/pop realm (i.e. try to dumb down your posts
). Thanks.
There have been a bunch of threads here at TB recently about how to learn a song "by ear," and some of us have pretty much been saying, "Just &$#%! do it." Well, that's easy to say, but if you know nothing about music, that's a pretty tall order (it's even tougher if you're lazy and stupid, but that's a rant for another day
First of all, learning a song by "ear" isn't learning a song by ear at all - it's learning by BRAIN. Your ear can't analyze anything unless your brain is engaged. And even guys who don't have formal theory training are STILL applying what they've learned informally through experience. But if you know a even a little about how songs are put together, it makes your life a lot easier. So, there will be some basic theory involved in this. Please do not be frightened - it DOES NOT STIFLE CREATIVITY IN ANY WAY. Don't buy into that crap. You will still have a 48" vertical leap and it will not cause your tattoos to fade. This approach presumes you know at least the BASICS of music theory - key sigs, time sigs, major vs. minor, etc. If you don't, come back when you do, okay? No one is going to spoon feed you.
Anyway, here goes:
TUNE YOUR DAMN BASS: Okay, you vets are laughing, but I learned a long time ago that NOTHING is too basic. The reason for this step should be obvious. If it's not, SELL YOUR BASS RIGHT NOW. Please. [NOTE: Some artists, for a variety of reasons may be tuned slightly off from A440. If so, tune to the recording while you're learning the tune.]
Figure out the key and time signatures: Okay, I already lost some of you. Sorry, but if you can't figure out the key and time sigs you are doomed to a lifetime of hunting and pecking on the fingerboard looking for the right notes. The time sig is 4/4 for most rock/pop tunes, but it can be anything from 5/4 to 6/8 to 37/64 if it's Rush
IMPORTANT NOTE: If the starting note is Eb, and the tune is less than ten years old, it's likely the instruments are tuned down a half step (Eb,Ab,Db,Gb). If it's in D, there's a good chance it's in "Drop D," which means the E string ONLY is tuned down a full step (D,A,D,G). Personally, when I played a four I would tune 'em all down in drop D, because I think drop D is stupid and didn't like having to think about where the notes where, although that does make the fingering trickier. The point of drop D is so the guitars can do their stupid "power chord" root/fifth thing (D/A/D). Creed especially is guilty of this. Beware.
Figure out the chord progession: [Note: If we were talking about jazz, this step would be before figuring out the key signature. But we ain't, so it isn't] Figuring out a tune note by note is doing it the hard way. Figure the chord movement out FIRST, THEN go back and fill in the connecting notes. When you write a song, that's how you do it, right? You have a chord structure and you create a line that fits that structure. So learn the tune the same way. If you are having a hard time hearing the bass line, listen to the rhythm guitar changes. It also helps to know simple chord progressions: I-V-I, I-IV-V-I, I-vi-ii-V-I, etcetera. That is, if it starts on I, your next chord is likely to be V, if you're on V, your next chord is likely to be I. After a while, you'll be able to hear the intervals yourself. But take the time to figure out the overall chord progression and WRITE IT DOWN. And if you just write the changes (I-IV-V-I) instead of the root notes (C-F-G-C), you can refer to it to play the tune IN ANY KEY (Holy versatility, Batman!). I'm not going to get into things like alternate key centers (V's suddenly acting as I's, etc.), but realize they exist, and can make your life hell. Also, in a lot of blues-bases stuff, EVERY chord is a dominant seven (I7-IV7-V7-I7, etc.), which technically means nothing really resolves. This may bug purists, but try not to let it ruin your life. Just play flat 7's.
Figure out where the guy is playing on the neck: I can't overemphasize this point. If you can figure out where the guy is playing on the neck, it'll give you a much better idea of what your note choices are. Bass players are as lazy as anyone else (no!), and don't generally make giant intervalic leaps if they don't have to. This is the biggest problem with tab, IMO. You see how someone tabbed something and you KNOW the guy who is playing on the CD isn't doing anything like that - he'd need three hands. YOU SHOULDN'T BE LEAPING ALL OVER THE NECK. Would you write a tune like that? C'mon. And if you can figure out HOW he is playing, you'll have insight into WHAT he is playing. Listen to the tone. Is it growly? Then he's down on the lower frets. Is it round and tubey? Then it's further up the neck. Is he using open strings? Is he playing a five? Is he using a pick? All of this stuff will give you a clue. And if you 'scribe a lot of stuff by the same guy, you'll start to learn his habits and cliches as well. Even guys like Geddy Lee and Les Claypool (okay, ESPECIALLY Les) end up playing the same crap over and over. They're human too.
Connect the chords: Now it's time to connect the chords. There are lots of ways to this, and this is where there is likely to be the most debate. But what you want to figure out is how the other guy did it, regardless. If you want to learn the tune note for note, then this is where the dirty work is. But if you know the key and the chord progression, your job is made MUCH easier. Start with chord tones within the key (1,3,5), then other tones within the key (2,4,6,7), and if none of those are working, go with chromatic tones (notes outside of the key). If it sounds particularly "jazzy," there are probably a few notes outside of the key sig (esp flat fives/sevens). If it's a simple blues-based tune or something where the bass line isn't particulary prominent (or if it just sucks and you think you can do better), you can get away with creating your own line based on the chord progression. Again, lots of ways to do this. I tend to think modally (see other threads on modes), but to each his own. Just remember that if you work too far outside of the key sig you're gonna end up with "Donna Lee," and God Knows We Don't Want That.
DON'T GIVE UP!: This is probably the most important advice of all, and has been given a zillion ****ing times here and no one seems to listen. This all takes time. You won't be able to do it all overnight. If you want to be any good at this, it can take years. But if you don't buckle down and DO IT YOURSELF, you will never, EVER be able to do it. And asking people to do it for you is not only lazy and rude, but is just hurting your own progress as a musician. THERE IS NO EASY WAY. So quit asking.
Anyway, I think that's about it. Again, this is all very generalized, and makes some fairly broad assumptions, and doesn't deal with avoid notes, alternate key centers, modes, body piercings, etcetera. But it should at least give you a methodic approach. I certainly invite others to clarify or add their tips. But let's try to keep it constructive, and if possible directed more at the rock/pop realm (i.e. try to dumb down your posts