I have had students help me brainstorm categories for the rubrics. I then decided the point values and specific descriptions for each point value. Sometimes I asked them for their input, but I always had the final say.
Have you seen Rubistar (a free online tool for creating rubrics)? This site is great and so easy to use. You could pull it up on your Averkey (project what's on your computer to your classroom TV) and use this as a guide to do it as a class.