Um, I'm gonna offer some tips on beginning bass...
1) Most of the comments here about timing involve the attack of the note; I believe real bass technique involves the "note-kill." NOTHING sounds worse than two bass notes (no matter how in-tune these notes are) playing at the same time. Yes, there are exceptions, especially on octaves and low/very-high notes, but for the most part, if you're striking a note and the prior one hasn't stopped ringing, it's going to sound like SHIT. So... learn how to stop the sound (depending on where you're going, you'll use either the left or right hand/fingers, but practice will dictate this).
2) Learn the intonation of your bass. Many folks tune open-string and don't bother checking what the 5th or octave sounds like... you don't necessarily have to get your bass "fixed" if the intonation's off, just learn which direction to "push" the string for your bass. (on this, I'm talking about pulling the string away from the bridge or pushing it towards the bridge with your left hand. you'll be surprised at how much traction those left fingers have on a string).
3) You'll end up using your.... shit, what are the names of the fingers? If you put your left hand palm-up, and assign numbers to your digits starting from the thumb (which is "1") towards the pinky (which is now "5"), you can see the "2" and "4" digits ("1" and "3" fingers? hm.). Anyway, those are the ones that are gonna get used the most, and the ones that'll probably get skinned a bit for the first month or so.
4) Don't worry about the 3rd. It rarely comes up. Practice 5ths, 7ths, and octaves. If the 3rd DOES get used, it's generally in transition or sustained-chord "exploration."
5) Learn this: 1-5-8-7-5-4-2-1. Most fundamental bassline ever. Lotsa variations, easy to learn, too. Do it in one "position," which, to a drummer, is "not moving the hand up and down the neck."
6) When you record, just run the bass right into the deck. The bass is somewhat magical in that it sounds great straight in, no EQ. No shit.
7) Amps. Um, I got lucky, mine sounds great. Maybe someone else here can offer tips on amps, cuz I don't have much experience with them.
8) Most basses use active electronics, which, to a drummer, means they use 9volt batteries. If you start getting distortion for no reason, it's time to change the batteries.
9) New bass strings sound like shit. They're bright and don't characterize the "bass" at all. They'll lose this after a couple of weeks, don't worry. Once they're broken in, bass strings last FOREVER. Unless they break, don't worry 'bout 'em. Besides, by the time you can tell when to change strings, you'll have bought a better bass anyway...
10) I recommend Jazz basses, they're easier to fret (IMHO). If you're interested in slapping the bass, look into a Precision-type bass, the strings are further apart from each other and easier to hit individually.
11) The bass is a FUCKING HEAVY instrument. Expect your back to hurt for the first month or so, if you're gonna strap one on. There's nothing wrong with sitting down and playing the bass, it's just weird to see the bass player (if it's not jazz-style music) sitting down at a show.
That oughtta last you a couple of months, hope it helps!