It's hard for a restaurant that's not affiliated with a national chain to make it unless they have something very special. Quality of food and service are definitely the top contenders for gaining repeat customers.
But some of the best food I have ever had came from a restaurant where I never really felt comfortable or welcomed. But I have a place that I go to often and recommend to everyone where the food is mediocre but the ambiance and the attention is spectacular.
The owner of this Mexican restaurant always comes to the door to greet us. If he misses our entrance he will stop by the table to shake my hand. He treats us like we are his best customers and we really aren't. The bartenders and long-time staff do the same.
It's the owner and staff's personal attention that brings us back time and again and keeps us recommending this establishment to everyone coming into town to visit.
So business owners and professionals, single out your customers and learn their names. Take time to ask them about their family. You'll not only gain a friend but a loyal and appreciative customer.