On a PC, you can take screencaps by hitting the "PrntScrn" key on your keyboard, then pasting that content into an image editor (like Paint).
On a Mac, you can take full screencaps by hitting CMD + SHIFT + 3 (will save as .png on your desktop) or take a selection of your screen by hitting CMD + SHIFT + 4 and selecting a portion of your screen within the crosshairs (will save as a .png on your desktop). You can change the default save format in terminal with
Code: Select all
defaults write com.apple.screencapture type image_format
Please shy away from .bmp and .tif image formats (we don't all have FiOS and some of us have usage-based billing). .png is your best bet, and the artifacts in .jpg's tend to make them look bad. .gif's are kind of out of the question.
Popular image hosting services include imgur (preferred), min.us (preferred), Imageshack, and Photobucket.