Be reasonable with your requests. Be reasonable with your responses. Human actions (at least, in professional and business fields) are mostly driven by reasons. People never (or very-very rarely) do something out of spontaneous wish at work.
Yes, you can have a spontaneous idea, but it, anyway, will serve some particular purpose. Idea tries to solve a problem, and the is the reason why you do that - you want right the wrong or make something better.
Often times in order to do what you want to accomplish, you will need to request something from your fellow colleague. Usually, you will need to have it done by certain deadline. This is where the interesting part begins.
You know exactly why you want something to be done by certain date or time. But are you sure your fellow colleague, from whom you request, comes to know that by reading your e-mail? Does he get why this needs to be done today? Is it in any way more important than what he is working on now? Unless he is a powerful mind-reader the answer to all such questions is "No!". E-mail just does not bear with itself enough of the mental energy to discover all of that!
Do you want you request to be handled in the best possible way? I bet you do. So, be reasonable. Write you request in a best possible way. Explain why there is a need to do something and why deadline is such as it is. Do not send unreasonable requests!
Same line of thought applies to responses. And even if you receive an unreasonable request - there is a reason why it went out. Help the requestor. Ask him questions. Unreasonable response will just turn into a dead-end. Often quickly bricked up behind your back while you drive there.
Do your best to explain your reasons and understand reasons of others. If you are not sure if you were understood correctly - follow-up your e-mail with a call.
And be reasonable with what you write and what you say.