I'm going to share a little of my experience job hunting as a student. I struggled a little at first but luckily I found a lot of good information that I want to share. When I was submitting my college student cover letter to potential employers I tried to come across as a professional. Even thought my resume didn't have an actual list of past employers related to the position I wanted. I knew what to present on my cover letter and what to stay away from.
If you're putting together a college student cover letter you should already have a resume put together. If you don't, get that done first, that's the best way I found to approach the letter. My letter would make reference to the resume so it helped me a lot to have the information I was going to present all written down and it just be a matter of presenting it with a well written letter.
As a student, I didn't have much to show for work history. I had a few part time jobs but none at the time I was sending my resume and cover letter. I was aware of this when I was writing my college student cover letter and even though the two jobs I had before weren't related to the position I was applying for, I put them down for reference and because they both involved the handling of money. Which I thought might help me come across as trust worthy.
I wrote a custom college student cover letter for every company that I applied too. On every letter I emphasized how punctual and responsible I was and made reference to my classes and attendance. I did this because I had read that one of the biggest problems employers have with students is the number of missed day and constant excuses for not showing up. I needed to paint a picture for them and I felt the best way to do this was by making reference to my attendance of classes.