Start from this article (slide show) how to increase ASP.NET perfomance

http://www.slideshare.net/oazabir/10-performance-and-scalability-secrets-of-aspnet-websites#btnNext

10 ASP.NET Performance and Scalability Secrets

machine.config

<system.web>
  <!--<processModel autoConfig="true"/>-->
  <processModel autoConfig="false"
    minIoThreads="101"
    minWorkerThreads="2"
    maxIoThreads="200"
    maxWorkerThreads="40"
    />

[HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\ASP.NET\2.0.50727.0]
"MaxConcurrentRequestsPerCpu"=dword:0000000c

http://blogs.msdn.com/b/wenlong/archive/2008/08/13/orcas-sp1-improvement-asynchronous-wcf-http-module-handler-for-iis7-for-better-server-scalability.aspx

Contention, poor performance, and deadlocks when you make calls to Web services from an ASP.NET application

http://www.ckode.dk/server-configuration/tuning-iis-7-for-static-content/