If you receive a lot of mail, you'll be more productive in Gmail if you use keyboard shortcuts. A list of the shortcuts is available from Google, but Evan Williams has reformatted the list so it's easier to print it in one page. Don't forget to enable "keyboard shortcuts" in Gmail's settings.
Gmail shortcuts, printable version
Compose messages in Gmail efficiently
Fast ways to check your Gmail account
Top 5 Essential Android Wear Apps
33 minutes ago