By default, screenshots (cmd⌘ + shift⇧ + 3) are saved on your desktop. It is possible to change this default location of screenshots, use the following command:
defaults write com.apple.screencapture location [path]
If you want to save the screenshots into the ‘Pictures’ located in your home folder, change [path] to ~/Pictures
To make the command take effect, you need to restart the System UI server:
killall SystemUIServer
Revert to the default setting (Desktop):
defaults write com.apple.screencapture location ~/Desktop
Screencast:
Great tip!, would be nice if we could edit the default user profile to do the same thing for all users and not just the currently logged in user.