I used to tell my staff, every contractor does the same 97%. The difference between good and great lies in that last 3%.
Often, we complete the project, get the check and move on. The japanese culture taught me, we must learn to say thank you after the service is given and the payment made. It makes all of the difference in the world.
After all effort is expended and the contract is fulfilled, that last action is vital to the relationship and to our reputation.
Take the time to write a hand-written note to your clients. Tell them that you appreciate that they trusted you. Ask how you can do better the next time that you do business with them.
It will make them recognize that you are different than all of the others and are, indeed special. It is the smallest of efforts, but yields far more than much grander efforts on the front-end of the contract.