If you're getting crappy searches (this is a problem for a lot of people right now), click on LW's Connections tab (if you don't see a Connections tab, click on View > Show/Hide > tick Connections).

You'll see the hosts (ultrapeers) that you're connected to... right click on a host > remove. You can do that for all ultrapeers that you're connected to - they'll be replaced by new UPs. Does this help at all?

If results are reeeally sparse, try either deleting LW's preferences folder or deleting/replacing your gnutella.net file. There's info here (it's a connection probs thread but still has the info you need): If LW Will Not Connect

If your search results are full of spam, try this hostiles list - it might cut down on the amount of spam that you see: The TechNutopia Fullsize Hostiles List for BearShare and LimeWire