1. Keep It short
2. Use a descriptive subject rather than leaving it blank
3. Write with clarity and conviction
4. Get the recipient invested (talking/asking about their own research is a good way to do so!).
5. Include a call to action -- what do you want from them?
6. Make it easy to respond (e.g. include your own availability alleviates the need for emailing back and forth to find a time to meet).
There are many resources for help with writing on campus.
The Writing, Speaking and Argument Center can help you at any stage of the writing process. Whether you need a quick help sheet, or an appointment with a writing consultant, there are many resources available at http://writing.rochester.edu/help.