The way you treat people who come through the front door. It's your "secret sauce." Your work is always exceptional, but there are other exceptional car shops out there. The way you approach and communicate with anyone who comes through that door is what has kept my loyalty for 5+ years.
I've been going to this particular Precision Tune for years even after I moved across the city from them. They are professional and most importantly they have never tried to sell me a service or part that I know I didn't need. Also, their prices are fair. Highly recommended.
Prices always seem lower or at least even with comparable places, time is always taken to explain the work or recommend services without being pushy, and everyone is always friendly and as helpful as possible during already stressful situations with unexpected costs and repairs.