Demographic information helps build balance in programs. Most people are happy to provide it. Education level and major is like demographics, it tells where you volunteers are coming from. It can also be used if you need a volunteer with a specific skill. Ask people to provide a work and volunteer history.
Previous experience can help in appropriate placements for a new position.
Days, hours, one time event, etc. This is by no means the only information needed for a volunteer data base, but it is the basics. The challenge in developing a record keeping system is to select the best information and record and not record so much that the data base is running the office.