To volunteer as a marshal for a NASCAR event there may be a specific role that could get you accepted to any race they put on. As far as I know however, to be a flag or track marshal, each event is responsible for their own marshals. Since the majority of NASCAR races take place on ovals or speedways, few volunteers are required. NASCAR relies on paid spotters and fire crew to work specific areas. However for the few events that involve circuit racing NASCAR requires a large group of volunteers.
So how do you go about registering?
There are a few options however you will have to do some research. The most obvious option is to contact the event organizer: NASCAR. And you will probably wait for a while to hear back. Once you do, there is obviously no guarantee of being accepted. Be careful not to sign up for a volunteering role that doesn’t involve marshaling. For example a lot of volunteers are used for everything from crowd control/security to garbage collection.
The other option is to become a member of a marshaling club or organization. NASCAR relies on clubs like the SCCA. Membership there allows you to get the necessary training to qualify as a pro-event marshal. So that when registration opens, and a particular organization is selected to provide marshals for that event, you will be more likely to be accepted as a member of that club.
The final option is to contact the circuit where the event takes place. For example when I wanted to marshal MotoGP, the only contacts I could find were employed by Indianapolis Motor Speedway. So it was an obvious choice of first contact (this was before I learned of USAC). You may go as far as asking for a job with the circuit so that when the big event comes around you have the possibility of working there as an employee. This is the case with many New Jersey Motorsport Park marshals who were specifically employed by the track to work various track rental days, and who were also given an opportunity to work major events when the majority of marshals there are volunteers. Working for the track is not practical if you only want to volunteer weekends.
Best of luck and if you have pertinent information to share, please leave a comment below!