The syntax for disabling warnings is as follows:
#pragma warning disable 414, 3021
Or, expressed more generally:
#pragma wa
MSDN has a list of warning codes. Unfortunately, you have to click each link to view what the code actually means.
Look down the list of C# compiler errors and warnings to find the individual warning numbers.
You shouldn't need a list. The compiler will tell you. If you get a compiler error that says "warning CS0168", then add 168 to the list (or, better yet, fix the code).
FYI -
If you're using Visual Studio 2008, you can get the code directly from the Error List by right-clicking the error, and selecting Show Error Help from the context menu. The Help window should pop up, and show you everything you ever wanted to know about the error a la the MSDN website.
Could save you a bit of time.