A quick look at recent (past year) threads on copyright shows that we discuss theory, philosphy, and the evils of corporate capitalism a lot more than "proper use of tools" in this area.

The most useful thing found has been the recommendation (from several) that one may consult the BMI and ASCAP websites to search for whether they "administer" a particular song. (I'm assuming you're US based?)

It is to be noted that not finding a song there doesn't necessarily mean it's not tied up by someone, but if it is found there, you can be pretty sure you've found someone who wants your money.

John