I bought a new suit yesterday. Quite an expensive one, at that.
I don't need any new suits. I have a ton - I wore them every day for years - and they fill an entire closet. Other than a few speaking engagements per month, and an occasional dinner at a "jackets required" restaurant, they don't get any use.
However, when I walked into the store yesterday, a clerk immediately offered me a cocktail, my favorite spirit of all, no less - Bombay Sapphire - and of course I said yes! While my other half was trying on several dresses, I began browsing the suits, started trying them on, and found a few I really liked.
And, to be quite honest, I felt bad accepting a drink if I wasn't going to buy something. So, I walked out with a suit that cost the equivalent of many, many cases of Bombay Sapphire.
The lesson here is that if you obligate someone to you - meaning you give them something freely with no expectation of reward or gain - the psychology of obligation selling goes to work for you. Don't be like so many salespeople who only go out of their way for a prospect when an immediate sale is imminent. Instead, give of your time and talents freely, and the sales will start pouring in to you almost immediately.