My wife was shoe-shopping. A friend told her to try this shoe store at the mall. You all know the kind of service found in a mall chain store, right?
The sales clerk happened to also be the manager. He was thoughtful, engaged, knowledgeable (all words my wife used to describe him). He asked questions, listened to her, brought her shoes that matched her needs. All the things you expect a good salesperson to do, and especially the manager.
Here's the clincher...
While she was deciding whether or not to make a purchase, he picked up the shoes she had worn in and washed them.
He cleaned her old shoes. No expectations on his part, he simply picked up her old shoes and washed them with a special cloth. She was not yet decided on making a purchase, but that definitely closed the sale. Yeah, she's talking about this experience to everyone she knows. Totally unexpected service that costs the store almost nothing, but buys the store a ton of advertising.
That is WOW!
PS If you are a jewelry store you should be cleaning the rings of every customer who walks through the door. If you are a stroller store you should be lubricating every squeaky wheel. If you are a store that caters to moms and babies you should have a fully-stocked changing station. What unexpected simple little nicety can you offer?