Random ideas from me and others -- the overarching concept being to entice the customer to come to you first rather than the other way around.
1. "Have breakfast with the customer" -- a former boss taught me this. Excellent salesman, he thought from the client's perspective at all times and actually did have breakfast lunch and dinner with them.
2. "Let it be their idea"--another former supervisor who was brilliant at this. I don't know exactly how she did it.
3. "Solve their immediate problem well" and then they will call you to solve others - e.g. sell them stuff they need.