When paper troubleshooting I try to go through the code methodically:
1st: Stupid checks, First I go through and check for proper semi colons, and correct number of and matching brackets
2nd: Scope and variable errors, next I check for proper scoping and declaration of variables
3rd: I run through the program line by line and "run" it in my head line by line.
That should get you to get most of the answers, if not all.
-Mal