is it humming? crackling? if it's humming, you are getting electrical interference from something close by. best bet is to make sure your solder looks shiny, not a dull gray. another thing could be that you need to shield the inside of the control cavity. and the back of the pickguard if its a strat. check all your connections. stew mac sells shielded wire to wire up your guitar if you need more wire. that stuff really rocks. used it in an old guitar that i don't have anymore and it really helped with noise. an too, if a pickup hasn't been fully potted (dipped in 150 degree wax), it will get noise too. and one more thing, this might sound trivial, but check the tightness of the pickup in the ring. this may or may not cause anything, but a rattling pickup may cause some unwanted noise.