2013-03-13 Minimize cellular usage on iPhone

There's a number of guides on the internet that talk about minimizing cellular usage. Often, they go into generalities, like "don't watch streaming video". Well, duh. I'm not going to offer general tips, but instead list a few settings for the iOS and some popular apps so your iPhone (or iPad) prefers WiFi whenever possible.

In the Settings app:

Separate apps:

There's some things I'm not sure whether they use cellular data, but I'm listing them here:

Edit: there's a much better, much longer list here:
TidBITS: What’s Behind Mysterious Cellular Data Usage in iOS 6?
TidBITS: Mysterious iOS 6 Cellular Data Usage: A Deeper Look