Home sharing
I had difficulty setting up Home Sharing with my iPad and AppleTV using iTunes 11.0.1. The instructions indicated to go to the advanced tab, but this was inaccurate. Fix: go to iTunes-->Preferences-->Sharing and select "share my library on my local network". Then go to File-->Home Sharing and select "Turn on Home Sharing". This fixed my problem - Apple's written instructions in the AppleTV Gen 3 manual were not current for iTunes 11.0.1.
ITunes 11.0.1-OTHER, Mac OS X (10.6.8)