Include a call to action. Clearly state the required action and deadline. This is more effective than a simple request for feedback. If no input is required, let recipients know that the information is just for their files. Include contact information.
Many business people look for contact information at the end of an e-mail.
This can be a quick, convenient way to access a phone number. Every time you send a message, this information will be included. Say hello and goodbye. The words you use to sign off should reflect your relationship with the recipient. Avoid excessive formality.