There are two incredibly effective marketing techniques both involving the creation of throw-away value propositions to get someone to accept another, related value proposition. The first one is the foot-in-the-door technique, where the throw-away proposition is relatively non-committal, and the related proposition is more involved. The idea is that getting someone to accept the throw-away proposition mentally prepares them to accept the later related one; since the person already has dealt with you, there's less transaction anxiety.