What you really want to use is music that is A) Recorded very well (yes Steely Dan is fine, as is Acoustic Alchemy, Doobies, pretty much anything very cleanly and crisply mixed) B) Something from the "A" category that you know inside and out in reference to how it should sound on a very nice system.
Bassman1958 has the real answer to how you really do this. After I dial a system in using my IVIE IE-45 RTA (I actually design and tune sound system for performance as my "day job"), I spin music that is appropriate for the type of music being used in a venue. I love to use old The Call tunes for confirming any delay settings since they always had a very punchy mix with lots of space. But I usually drop in music that I don't play but do understand well as my final "tweaking" tunes.
These days there are relatively inexpensive Apps for RTA's that while not dead accurate, do get you in the ballpark. You can find pink noise wav files online and convert those to a CD (never use your ipod/mp3 player for this unless there is no alternate, bottom line an MP3 file unless jacked to 320bp's is just not that great sounding unless you are blasting your ear buds).
So anyhow, hit that wav file through your PA and try to adjust your EQ so that when you look at your RTA App, the EQ looks flat in the middle. This what is known as getting a flat response. From there when you start bringing your mics into the mix, should feedback occur, again use the RTA App to identify where the feedback is happening (it will be the LED bar that goes waaaay up when the feedback happens) and then reduce that offending frequency on your EQ.
While this isn't perfect by any means, you'll be a long way closer to having good sound than by just spinning a tune and trying to make it work for you.