How to capture a screenshot of a movie

DesiTorrents has a terrifically helpful FAQ page that I'll be pointing to on the Darknet resources page (if I ever find time to build it). Here's one snippet:

How do I capture a screenshot of a movie?

Here is a method for creating a snapshot from your movies for both realplayer or windows media player! Please use one of these two programs for creating your snapshot!

For RealPlayer, you will need to turn off the optimized display. You can do this by running RealPlayer, clicking on View -> Preferences, going to the Performance tab, unchecking the box labeled "Use optimized video display", hitting OK, and restarting RealPlayer. Now you may make take a screenshot by pressing the [ALT + PRNTSCRN] combination. You can paste this screenshot into any graphics editing program (e.g. MS Paintbrush) and save the file. When you are done taking screenshots, you should re-enable the optimized video display because this makes videos play smoother and look better.

For Windows Media Player, you have to disable Hardware Acceleration. You can do this in Windows Media Player 6.4 and later by clicking on View -> Options and moving the Hardware Acceleration slider to None. You can do this in Windows Media Player 7 by clicking on Tools -> Options, going to the Performance tab, moving the Hardware Acceleration slider to None, and restarting Windows Media Player. Now you may make take a screenshot by pressing the [ALT + PRNTSCRN] combination. You can paste this screenshot into any graphics editing program (e.g. MS Paintbrush) and save the file. When you are done taking screenshots, you should move the Hardware Acceleration slider back to Full because this makes videos play smoother and look better.

For Mac, with the movie in normal size (not the cmd-F fullscreen size, just for better quality and smaller image size) just pause the movie when you want, in most of software with space bar, and hit cmd-shift-4 (the upper 4, not the numeric pad). A cross will appear to let you select the part of the screen to capture. (Note: with 3, you capture the whole screen).
It will create a .jpg .tiff or, most probably under OSX, a .pdf file on your desktop. As it's customary to send jpegs here for that kind of things, drop it on any graphic application (Photoshop style, but even Preview will do) and save (or export) it as a jpeg with a quality of 50 on 100 -- or 5 on 10.