How to write a review : Writing a good review is a task that requires significant effort and practice. A good review should be able to bring out the key strengths and weaknesses of a paper. You can look up plenty of resources available on the web on writing reviews for computer science papers. For example, here is a collection of links posted by Michael Ernst.
At a high level, a review should cover the following key points:
When to submit: All reviews should be submitted by mid-night before the class next day. Each student can also read and rate reviews posted by others.
How to submit: You can submit your reviews through this website: http://irdb.app-ns.mpi-sws.org/