There are heaps of spam/junk files on the network. Do you use the junk filter? It's not perfect but it does help with weeding out crap. The thread below's old & very long but has good info & tips.
Junk Filter

Also try using The TechNutopia Fullsize Hostiles List for BearShare and LimeWire

Have a look at the thread below, it has tips for searching (video as well as music) Make sure to check out the bits about adding words to the keyword filter...that will help to exclude some crap from your search results!
How to find music