Of course you should avail yourself of all TB links such as the ones above to learn more about proper bass setup. But here's my two cents worth.
Start by measuring the neck relief. It is critical that you resolve any issues here before attempting to raise or lower the bridge saddles. There are tons of people who will tell you how to do this "by feel." I disagree. Get a set of feeler gauges from your local hardware store for less than $10 and measure it as God intended. Capo the 1st fret, hold down the fret where the neck meets the body, and a .012 gauge should barely slide under your low E at the 8th (or so) fret. If it slides in between string and fretwire with room to spare, you have too much relief. If you can't slide it in without raising the string, you have too little. Is .012 the magic number? No. Try .013 and .011. If you have a five string, maybe even .014. The point is, measure it.
The truss rod counteracts the string tension. If the strings are winning too much and there's too much relief, righty tighty. If the truss rod is winning too much and there's not enough relief, lefty loosey. 1/4 turn at a time or even less and then tune up and measure again. Get this adjusted correctly before adjusting string height at the bridge saddles.
After having done this, adjust the bridge saddles. Get a metal ruler that shows 64ths of an inch. No capo, no fretting. Just measure the distance between bottom of string and top of fret. I like the 12th fret here. Your low E should be 5/64s. This measurement can taper down to 4/64s at the treble end.
After having done these two things–neck relief and string height–check each string up and down the entire fretboard for any buzzing. If there isn't any, you've won. Congratulations!