Optimizing IIS server
After searching the web for a while, I found some useful tips for optimizing Microsoft IIS performance.
The first thing to do is disable logging for your sites. Since you're interested in performance you have to be on a production server and there's no reason to have logging enabled.
One other thing to do is adjust the CPU that every application pool can use. You can even have the server terminate an address pool if it's using to much CPU.
You may also set the keep alive limit so you'll have less sessions.
I've also excluded the inetsrv directory (located in system32) from antivirus scans.
In my occasion there was no need to limit the bandwith for a website since there was no problem with it.
You can always speed the server up by improving the overall performance by disabling unused services or excluding application folders from antivirus scans (only when it is absolutely needed, like on MS SQL or Exchange servers).