Recommendation letters from professors are among the most important tools in the hands of admissions committees to evaluate your application. Here is a sample reco letter - written about a good student by his professor.

To Whom It May Concern:
It is a real pleasure to write this letter of recommendation for Vinay Hegde. Vinay is an extremely
gifted student, among the very best I have had the opportunity to teach and work with here at XYZ College.
He has my strongest recommendation for admission into the Stanford Master’s Program.
I first met Vinay as a student in my undergraduate Operating Systems course, CS161, in Spring 2005.
CS161 is widely regarded as one of the most difficult courses in Computer Science (if not at XYZ College in
general), since it requires a great deal of programming — students design and implement their own
operating system. This course exposes students to an intense software design effort that is not found in
other courses. Generally only the most talented students stick with the course and do well. Vinay did
incredibly well in the course, ranking 3rd in the course, just a couple of points behind the top two
students, with an overall grade of 91 out of 100. He demonstrated very strong technical skills and pulled
most of the weight on the programming assignments (which were done in teams of two). This alone is a
very strong endorsement for his abilities.
Vinay also took my graduate course on Wireless Communications and Sensor Networks. This course
involved reading and reviews of advanced research papers as well as a significant research project.
Vinay did extremely well in the course – he made an A and scored the 4th highest grade in the course,
which is significant considering that his was a Ph.D. level seminar and Vinay was still an
undergraduate. His paper reviews were very lengthy and detailed, indicating that he really absorbed the
material, and his final project (on resource allocation in wireless networks) was among the best in the
course.
I also co-advised Vinay on his senior thesis research project. Vinay took on a very ambitious and
somewhat risky project, that of using ideas from economics and game theory to allocate bandwidth in
wireless networks. In many wireless and sensor network contexts, multiple users or applications must
share the very limited bandwidth. Vinay developed techniques for fairly allocating capacity across
multiple flows using real-time auctions to trade network capacity for data quality. This is an exciting
project and Prof. Limaye and I have continued working in this vein since Vinay graduated.
Although Vinay is somewhat shy and quiet in person, he is very intelligent and in our weekly research
meetings he is really engaged and has many ideas to share. I have no reservations
giving Vinay my highest recommendation. He is a real star and I highly recommend him for your
program.
Thank you,
Prof. Amit Bansal
XYZ College