I concur with what Zur and Jacks listed above. A few other recommendations for consideration.
1. Avoid listing an email account with a bizarre or non-professional name (e.g.:
bonghit420@youruniversity.com,
fastdriver2000@hotmail.com). An email account that uses your name or a combination of your initials is good.
2. If you list a phone number, make sure you check it regularly for messages (in some cases this can literally make the difference between getting an interview and being passed over as someone who is too hard too reach).
3. When listing education (in addition to degree/certs), don't list class names, list the topics covered (e.g. Integral and Differential Calculus, C++ Programming).
4. Do some research on who uses your prospective employers products or services. If you have any experience with their products or services it would be good to mention (lets them know you are at least somewhat familiar with their business). This lets them know that you are serious about the position and are not just "shotgunning" out your resume/letter.
5. If there are any industry standard practices (ISO quality standards etc.), software packages, or other tools that are likely to be used by the employer that you have experience with make sure to mention them.
6. Triple check the cover letter and resume's spelling. Have other people read your letter to insure that you haven't maid any obvious grammatical errors as I've not done here. Little details like these get "stuck" in interviewers/raters mind's
If you get an interview, here are some other recommendations. I've had the opportunity to sit in on a number of interviews seeking to fill positions (full time and student internships) where I work. Some of the items that I found most attractive in prospective coworkers/employees/interns:
1. Present a positive attitude!! If you mention negative situations (difficult coworker interactions, problems during team projects in school, past negative employment actions) be prepared to follow-up with what you learned from that experience.
2. Employers like people who demonstrate the ability to learn new skills and adapt to changes. Although it may not be the right thing to list on your cover letter I'd recommend having a couple of examples ready of situations where you solved some sort of project or problem that required learning how to use a new skill/tool/process/knowledge resource (new software program, how to utilize some industry standard or information database).
3. Have some medium-to-long term goals (that could generally be related to work) ready to list in case you are asked (the fact that you are interested in pursuing your master's degree would be a good one to mention as it relates back to item #2 above).
4. If asked about personal information (marriage status, children, finances, hobbies) be very careful about what you mention. Even though I don't think any employer can legally use some of that information to deny you employment, it can subconsciously "color" their impression of you. (e.g. a casual, or even joking, statement that that you "are a swinging single who parties hard, and stays out late,... but you always make it work on time" would almost assuredly make you look less desirable compared to another equally qualified candidate who did not mention anything like that). Assume that they will google your name to see what shows up!
5. Speak clearly, don't mumble, and go ahead and ask clarifying questions if you are not quite sure what they have asked you (it is kind of embarrassing to realize that you've spent the last three minutes answering the wrong question).
Much of the above is probably obvious and may not be applicable to many positions, but I hope it at least gives you some other "stuff" to consider.
Good Luck!