You might count the participants at various sessions. You might hang out at certain sessions to assist the speakers with handouts or equipment. Not much, but we'll do what we can. There are often fewer volunteers than we have jobs, so we have to prioritize. This issue is driven by conference needs.
Some time periods are busier than others.
We'll take your preferences into account whenever possible. When you register as a student volunteer, you'll specify when you plan to arrive and leave the conference. Within those constraints, we'll make some initial plans. We realize that things may come up and will try to make dynamic changes as needed. In turn we ask that you be as flexible as possible.