Hypnotic Mind

What are some ways to hypnotize someone without telling them there being hypnotized.?
I heard you can't hypnotize someone against their own will. But, I think I've done it to many people.
For example: I'm trying to sell someone a product and, as I look into there eyes; I say in my mind out loud:You will buy no matter what because this is how it is and will always be. It seems when I do the preceding my chances of getting a sale are greatly increased. Do you think there's some hypnotic activity going on? Or just a coincidence.
I think its...kinda like a placebo effect. You think it'll increase the chances of getting a sale, but it actually doesn't.
Scientology IS Hypnotic Mind Control Part 2