I'm a big fan of keyboard shortcuts. They save time since you don't need to move your hand from the keyboard to the mouse to make something happen.
To use shortcuts in GMail, first click Settings (upper right), and then pick Keyboard shortcuts on. Go back to your email; you will now be able to use these shortcuts. Start by picking a couple of commands you use often (like c for Compose, or shift-c to compose in a new window), and add others over time.
