Apple Logic Pro /LogicExpress Discussion

Hey guys,

I've been following the discussion you guys are having, but the 
philosophical aspect of it frankly doesn't help me at all.

But I do have a question:

Say I've written something, a song, a film cue, anything, where do I 
go or who do I ask whether I'm infringing on someone's copyright? 
Even though I consider myself having a broad knowledge on music I am 
also very aware of the fact that there are at least 20 times more 
works out there than I know.

How do you guys deal with it?

Cheers
Hans