.net performance test guid

1.On the process/best practices: I recommend 2010 book ".NET Performance Testing and Optimization - The Complete Guide", by Paul Glavich, Chris Farrell". It describes complete ASP.NET performance testing process and many best practice tips.
Microsoft's 2004 manual "Performance Best Practices at a Glance" in Chapter 16 "Testing .NET Application Performance" lays down main performance testing steps, but set of tools is outdated.
2.On the tools: It is essential to use at least one tool from of each of 3 groups.
Performance and memory profilers:

• CLRProfiler (free);
• Visual Studio 2008 Team Edition (and VS 2010) has a built-in performance and memory profiler;
• Red Gate's ANTS Memory and Performance Profilers;
• Micro Focus DevPartner Studio Professional;
• dotTrace Performance and Memory profiler that you already know.

HTTP traffic and client tools (free):

• Firebug / Yslow for Firefox;
• HTTP Watch (Fermium);
• Internet Explorer Dev toolbar;
• dynaTrace AJAX Edition;
• Fiddler.

Load testing tools:

• VSTS 2008 (and 2010) that you mentioned;
• NeoLoad;
• My company has a free Fiddler extension called StresStimulus that is not nearly as complete as the two above, but is handy for quick and easy load testing.