How do I set up wireless printing on my ipad2?

You need a compatible AirPrint wireless printer which will set itself up automagically. Otherwise if you have a Mac running 10.6 or later there is an application called AirPrint Activator which will allow you to share any printer connected to a Mac on your wireless network.

Here is the link for the download with a very easy to follow setup guide and video.

http://netputing.com/airprintactivator/

This is an option for Windows 7 but I haven't used it myself so I don't know how useful it is:

http://www.coveringweb.com/2010/11/enable-airprint-on-windows.html