Check the appropriate magazines, such as Lowrider, Truckin', and Super Chevy. Check the Yellow Pages. Choose three to four shops you can investigate. Find out what brands of air bag the shop carries. Ask to see work that the shop has done.
Most competent shops have a photo album displaying their work.
Look at the photos and ask the salesperson to explain the procedure shown in the photographs. Ask how long the shop has been in business. Ask about guarantees and warranties. Good shops will have a warranty on parts and a lifetime guarantee on labor. Choose the shop where you are most comfortable.