I’m writing this down so I won’t forget.

First, there’s the utility “Grab” in Applications/Utilities. It doesn’t have a window, you use the program menu or the keyboard shortcuts. After you take a shot it pops up a window with the image that you can save anywhere you want. By default it outputs TIFF images.

My preferred method is to use the keyboard shortcuts built into OS X. It generates crisp PNG image files of the screen.

apple command key + shift + 3 will take a capture of the entire screen (or two captures if you’re running a dual-head setup) and automatically save it as a PNG file on your desktop. It will be named Picture 1.png, where the number is auto-incremented with each screenshot.

apple command key + shift + 4 changes your cursor into a bulls eye. Whatever you select ends up the same as before—a file with the same naming convention on the desktop.

apple command key + shift + 4 when you’ve got the bulls-eye cursor hit the space bar. It changes the icon to a camera. It takes a picture of the selected application window—the selected window will be highlighted in baby blue.