When working in any photo manipulation package, and especially when first starting out, it is very important to develop good habits. One habit you need to develop early is the use of shortcut keys instead of menu buttons. This will dramatically increase speed once you practice and get use to it.
To help in your quest for increased productivity here is a list of some of the best cheat sheets you can find for Photoshop, PS Lightroom, PS Elements, Aperture, and Gimp.
If you have any other cheat sheets you would like to share please leave a comment below.