Sorry to sound like an idiot, but how do I check the php error logs?

Thx!

I'm getting the same output (none - but a 500 server error). It's a fresh install of 1.5 beta. All I did was copy the files over, and make the 3 folders mentioned in the install docs, as well as the main install folder chmod 777. (I tried 775 as well). It just displays a blank page. I have no .htace...