Automatic saving may not be enough if you've just had the idea of the week (and you've been waiting for its arrival for the past 3 months) and you have to leave in a second and your brother is around the corner and he has that questionable look in his eyes. You need to save your message right now.
Of course, you can click the Save Now button, but in spite of the name that's a few mouse movements (where's the cursor?) short of right now. With your fingers on the keyboard and the focus on your typing you might as well use the keyboard to save the draft. And you can.
Save a Message as a Draft Quickly in Gmail
To save a message you are composing in Gmail fast:
- Press Ctrl-S (think save).
- Make sure the input focus is in the body of the message.

