Mine are in /home/mysitename/logs
And, you'd look for an error on that page. I was recently debugging something and got this:
Code:
[Tue Dec 16 12:53:04 2008] [error] [client xx.xx.xx.xx] PHP Warning: Illegal offset type in /home/mysite/forumdisplay.php(111) : eval()'d code on line 49, referer: mysite.org/newthread.php?do=newthread&f=4
So, I looked at line 111 in forumdisplay, found the hook name, then looked in my plugin for the problem.