http://www.west-wind.com/presentations/loadbalancing/networkloadbalancingwindows2003.asp
This guide is a very comprehensive walk-through on several key points on creating webserver farms, both in 2003 but this is also still relevant in 2008 (R2)
A small pointer here is that also there is an old MS article which states you should make a binding of you cluster IP on your IIS server so that it will accept the requests send via the clustered IP to that device.