OK,
1. Can you read music?
2. Do you have a keyboard?
3. Seen the Sound of Music?
Good. Your bass will work if you don't have a keyboard, but the keys might be easier for starters.
First, write out a c major scale on some staff paper (clef of your choice) and then play it on the keyboard. Here's where the Sound of Music comes in. Assign each note of the scale a syllable so C D E F G A B C becomes:
DO RE MI FA SO LA TI DO.
Now, for the very beginner it may be easier to start with the pentatonic scale. take out the half steps (the F and the B), and write this scale on your staff paper. You now have DO RE MI SO LA DO.
Play these notes on the keyboard and sing the syllables. Always read the music as you go. Start slow. Half notes or quarters, whatever's comfortable.
Good. Now, for various exercises.
Start with the first 4 notes, C D E G. and sing up and down DO RE MI SO MI RE DO. Work on this for a bit to get comfortable with the technique.
Play and sing intervals:
major 2nd: DO RE DO
Major 3rd: DO MI DO
Perfect 5th: DO SO DO
etc.
Once you're ready to add in your half steps, you can move on to arpeggios. Start with this pattern, 3 notes, up and down, starting with C D E D C, then move up to D and do the next 3 D E F E D, and so on:
DO RE MI RE DO
RE MI FA MI RE
MI FA SO FA MI
FA SO LA SO FA
SO LA TI LA SO
LA TI DO TI LA
then go back down
SO LA TI LA SO
etc.
Once you've mastered that move on to arpeggios:
DO MI SO MI DO
RE FA LA FA RE
MI SO TI SO MI
FA LA DO LA FA
And 4 note groups:
DO MI SO TI SO MI DO
RE FA LA DO LA FA ME
etc.
Remember, always be reading the notes as you practice these exercises. With enough practice you'll be able to hear and recognize intervals and patterns.
The next step is to get some simple music to sing to using the syllables. Since I'm only doing the major scale here, something like a beginner piano or organ book will do. Stuff like Three Blind Mice, Over The Rainbow etc. Play the piece and sing along.
When you've practiced all this, the next step is to start sight-singing it all. Go back to the first exercises. Play the low C on the keyboard and ONLY SING the rest. Eventually move on to the easy songs doing the same thing.
The point of all this? To develop your ears, of course. You'll start to recognize scales, intervals and patterns. When you hear your doorbell you'll know what interval it is! More importantly, your ability to hear chord changes will improve, which will improve your response time in playing situations. In addition you'll have unknowingly improved your reading skills!
So remember, always write out in standard notation what you're going to sing. Start out slow.
This is just the tip of the iceberg for ear training, but it's a lot of work that will really get you going if you put the time in.
Lastly, don't be afraid to sing! Don't worry about sounding like a doofus singing DO RE MI. You might destroy your family's ears, but you're improving your own.
PS this is all from memory here, so if I butchered anything, left things out or if there's anything to add to/subtract from it, please feel free to correct it!
