Looking for a good groomer can sometimes be difficult but knowing what signs to look for can certainly help.  Here are a few:

• groomer is certified
• clean and tidy facility
• adequate lighting
• open to tours of their facility
• kennels/cages of adequate sizes
• professional with clients and their pets
• keep records/pictures etc.
• other credentials (Vet experience, Pet First Aid/CPR Certified)

Most importantly, you should feel comfortable with the groomer you choose, first and foremost.