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.