Identify a racing series that with teams you would be interested in joining.
Find the Internet site for the racing series and any additional websites that may have forums for competitors.
Post to the racing forums for the series a note indicating your interest in joining a team. Include your abilities such as mechanical, electrical or logistics. Indicate your location and what tracks you would be willing to travel to with the team. Leave an email address or phone number at which you can be contacted.
When a team contacts you, they will most probably ask you to come to their location to help prepare for the next race. This is the time to demonstrate a willingness to help and what an asset to the team you would be.
Attend a race track in your area if you are not contacted by a team.
Post business cards that state your desire to join a team with your contact information. Areas around restrooms, timing and technical inspection will have bulletin boards for posting cards and fliers.
Make contact with as many participants as possible to hand out business cards. Ask if they might need help during the event as often a team will show up short a crew member and greatly appreciate a helping hand.