The only thing that saps productivity out of an organization more than meetings (Link)  is email. Has email ever helped you become more productive? Email has outlived its usefulness and has become the ugly drunk uncle no one wants to acknowledge or deal with.

Assuming you have to live with email in the workplace, here are 7 tips to help make it a little more bearable:

1. Start with the end in mind - Before writing your email, ask yourself what it is you want as an outcome to this email and decide if email is the right mechanism. If it is, make sure you write the desired outcome right at the start (e.g. Please approve, Please comment, etc).
2. KISS - My modified definition of Kiss here is Keep it short stupid. I don't have time to read your 12 page essay masquerading as an email. Keep all emails shorter than 10 lines. Anything more and your recipient will likely file it under "Never Read".
3. Never Reply All - Unless there is a very specific reason why everyone in an email thread should receive your words of wisdom, be judicious about who you reply to. Most people do a Reply All to protect their own ass. That's a horrible reason stop it now.
4. One Channel for each message - If you decided that email is an appropriate channel for your message in step 1 then please don't use other channels to pass the same message at the same time (printing a copy and sending it to me, talking to me about it in the hallway, etc). You chose it as a channel now stick with it.
5. Email doesn't convey tone - Remember that email doesn't  convey the tone of a message. Ask yourself if the message could be misconstrued without the  appropriate tone. If it can be misinterpreted then ditch email and use the telephone, videoconference or a good old fashion face to face. Countless issued have been created (tempest in a teapot) because the recipient over-reacted because he/she could infer the real tone of a message.
6. Time is your enemy - In my world, email is a nice to have and I read incoming messages about twice per day.. .and I am at least a week late with my emails. This means that anything that is urgent or time sensitive shouldn't be sent via email. Email is asynchronous. 
7. Archive IT - Set a time after which all email  get's archived (even if you haven't read it). I use a 1 - 1.5 week period then bam, everything get's archived. 

My core message is that I hate email. It is an ugly creation that punishes me every day. Remember that next time you punish your coworkers with it.