ASP.NET Webapplication unavailable on Live Environment - How to troubleshoot

I have a asp.net 3.5 web application which is deployed on server 2003 and IIS 6. After running fine for a few weeks it goes "Down" and by down I mean that when I try and access it the browser looks like it's load开发者_开发问答ing but never actually serves the page. After an IIS reset it loads quickly again.

My question is what are the steps and tools I should use in tracking the root cause?

First point of interest would be the event viewer, second the iis logs. If you still do not find the error then performance counters could help you out there.