You could also look for a program called MX Monitor, which will do the following:
Automatically add to the Ignore list anyone who is sharing few or no files, or anyone who queues more than a specified number with you.
Automatically start someone in your queue, if you are downloading from them.
Terminate the above upload is your download is cancelled.
Automatically start anyone whom you have on an autostart list.
I trade on WinMx a lot, but almost exclusively for video. It's much more geared to file trading, rather than waiting patiently in queue. If you see a file you want, check out what the other person collects, see if you have anything they might want, specify what you want, and where you are in queue. This might not work for mp3s, or it might work better, given the shorter upload time. Check for a chat room which matches what you're looking for.
I would consider the following to be excessive queueing:
More than two video files over 50 MB, or more than three total.
Anything in addition to a file of more than 300 MB.
Two or three mp3s more than you have queued yourself.
If you see someone in your queue with MxMon in their username, browse them and if they have something you want, queue it and it should automatically start.
