[Here are a series of screencasts that address specific items regarding classroom use of Google Drive and Docs. However, if you want a full Google Drive course, visit Lynda.com.]
Your life will be a lot easier if you create some sort of naming convention. This will allow you to readily identify the student and assignment (and class if you have multiple sets of students).
I use: period_assignment_lastname --> 3_DBQ_McDowell
In Google Docs you can add comments, participate in discussions (through the comments feature), and chat. Students can actively discuss collaborative projects, teachers can provide feedback during the development of the Doc, and teachers can annotate grades.