While I totally advocate using Firebug sometimes you need a starting point. I’ve been doing a few things that use prevent default to repress page loads. However, if something fails before the prevent default then it’s difficult to debug because the console is cleared when the page reloads. In order to stop this and to give me a starting point for places to put break points I’ve been using Tamper Data to abort page requests.
Whoops! I don’t do Firebug enough credit. Just click on the ‘script’ tab and select ‘Break on all errors’ in the options menu. Now it breaks on any and all errors. Sweet.