Im pretty terrible at this, In the past when learning songs I typically resorted to tab. Even my drummer has a better ear than me.(well, its sort of a joke as he used to be a piano player) Any advice on improving my ear would be nice. Thanks.

Sing what you hear.

A lot of it comes with experience and learning how to learn songs. Most songs in any given genre have their similarities and standard progressions - once you've learned them you can play by ear a lot better since you know the options of where the song might go.

For example, start by learning blues songs... pretty soon you'll be able to hear the difference between I, IV, and V chords and you'll be able to apply that to any other genre you play.

Sing what you hear.

Don't forget to play what you sing.

Also, practice practice practice. Your ear won't get better unless you exercise it. Learn everything you can by ear. TV commercial jingles, TV show theme songs, your little brother or sister's electronic toy music, anything you can hear.

Another thing I try to do is sing a note then play that note on the bass. The goal is to get it right on the first try. Also, close your eyes, play a random note on the bass, then guess the note name. These two in conjunction have helped me to some degree.

The trick with this is to it every time you practice. I did it for a week solid, where I spent 10-15 minutes at the beginning of my practice doin my exercise. At the end of the week I was getting good at it. Then I didn't do the exercise for a week or two. When I tried it again, I was as lost as when I first time I practiced this. So regular reinforcement will be key.

I believe it's critical in playing by ear to think in numbers as opposed to names. Don't worry about C, F, and G, but about 1, 4, and 5. That way, you're into the relationships among chords and pitches.

Sing what you hear.
Alot harder than said but there are numerous sites www.good-ear.com is just one of them
Here is a technique that helps try this everyday for 10mins by playing a major scale ( refer to sticky thread if you dont know the major scale ) but listen to each note ie: play the first note of the scale then before you play the next note of the scale sing it then play it to see if your singing of the pitch matches the note played.
I mean most of my students know the major scale inside and out but thats from playing by shapes or patterns which from years going over & over them lol without ever having to really listen to what they just played
And when you think youre ready after a few months you"ll be playing songs by ear in no time :D

I believe it's critical in playing by ear to think in numbers as opposed to names. Don't worry about C, F, and G, but about 1, 4, and 5. That way, you're into the relationships among chords and pitches.

intervals ... +1 on this comment ... the largest part of playing by ear (and improvisation) is interval recognition ... it would be great to know a note by its sound (pitch), but I dont think I could do this ... at least not nearly as well as I could learn to recognize an interval ... of course, being partially deaf and not hearing certain ranges doesnt help either ... so wear ear plugs when you play younguns' ... :).

play in the dark - fast track your ears and know your instrument

One technique I use for ear training is Sight Singing.

Take bass lines you already know and start singing them. Figure out what scale degrees the notes on the line are. That will help you to figure out the intervals in new bass lines your trying to transcribe.

Singing scales and intervals using numbers will get you there. Finding songs you are familiar with that start with the interval your trying memorize. Like Hot Blooded is up a 4th.

i suck so hard at figuring out songs by ear, i have to accidentally stumble on a part of a song to figure any of one out. i never put the work into it tho, wish i could make myself do it

When i played more guitar than bass, i would always listen to the bass to find the root note, then the chord from there. I generally can't just sing or listen to a note and name it but I can hear a note then play it on the first or second try. It can take some trial an error but I don't remember the last time I actually looked at tabs for a song. Sometimes hitting the wrong note helps because you can hear the beats and know you are close (play an A on the e string then a half step below the A an octive up, hear the beats? that's what i'm talking about). When I find the root note it's pretty easy to find the rest by listening to the intervals stated in previous posts.

Def practice this in the dark. With no visual distractions, Just the sounds and your position on the fret board. Eventually you will remember. But like Willplayforfood said, Reinforcement is the key. I dont think it possible to learn perfect pitch but you can certainly learn relative pitch, (pitches relative to the root)..Good Luck.:)