Not luck, just what you know about fake/infected files. I do have a few guidelines:

1) Add ********mp3.com to the blocked file contents list
2) Do NOT download anything under 350kb UNLESS it has full details (bitrate at the very minimum)
3) Anything that has no bitrate is FAKE because it can't be played.
4) And of course (unless you have a recent version of Limewire) DO NOT download anything that says update.