Gary Hewett wrote this excellent article on the difference between tricking people into buying versus gaining people's trust. The following paragraph nicely sums up the lesson learned:
If you are marketing a product and you want to be successful (hey who doesn’t set out to be a success with any new product?) then you had better plan to be in the game for the long haul. Take the time to let people get to know you. Give them lots of opportunities to experience you. Give them no reason not to like you. Prove that you have their best interests at heart. I believe this part is really vital: Research your product and practice your craft. Strive to be the best you that you can possibly be. Never “sell” a product or a service that is not beneficial to the buyer. Never “sell” a product period. Know them, know their needs, know what they want and give it to them in spades.
I heartily recommend you read the whole article. It is both interesting and entertaining.