In many states, you can take voting registration sheets and sign up new voters yourself. Once the forms are filled out, you mail them to the county election commission. Be sure to read the instructions carefully, and follow them exactly. One tiny error could easily invalidate a whole sheet of new voters. Lots of potential voters who are intimidated by the bureaucracy will register once you put the how-to information in their hands.
Gun clubs are a good starting point for voter registration.
Just as every gun club member should belong to the NRA, every club member should be registered to vote. In states with registration by mail, all it takes is about 20 minutes at a regular club meeting to distribute, fill out, and collect all necessary information for every single club member to register. In states which don't allow registration by mail, a gun club meeting can be scheduled during which to march the whole club down to the election commission, and register en masse. Gun shows and gun stores are other good places to distribute registration material. Gun store owners might want to put a registration leaflet in every customer's sack, and gun show operators might want to give such a leaflet to everyone buying an admission ticket.