But not all the bugs are easy to solve. The worst kind of bugs are hard/impossible to reproduce. For them my approach is to suspected places where it could occur and add logging, and just wait until it occurs again(sometimes it takes weeks or even months). So I am trying to log how the data flows through the system by isolating the direction to look for.
For example: I'm yet to find cause of the mystery of the MS Word and TinyMCE, where sometimes it will not strip out microsoft's formatting. It only occurs about once a month. I wrote a simple alert script which sends me an email when this happens and I can get to the person in seconds(most of the users are in the same office), and try to reproduce the exact moment when it occured on users computer.
My fix was just show an error asking users to repaste exact same text which then works as expected.