“Most people could cut their email output by ten percent or so and maintain or even increase their productivity,” writes Art Carden. Messages to cut:

• Questions you could answer for yourself. See what Google has to say before you send an e-mail that makes you look silly and wastes time.
• Responses to e-mails that CC you. Often, these e-mails are just informative, and don’t need an answer from you.
• Forwards. Yes, it’s a noble cause. So why don’t you take the time to compose your own personal, thought-provoking e-mail, and send THAT to your friends? They’ll appreciate it much more.

E-Mail: A Write It Well Guide has more great tips on boosting your e-mail effectiveness.