Being the mentalist I am, I immediately thought to hypnotism. No not the "you are getting sleepy" stunt, but a complex system that involves practice, study, and concentration.The brain is like a computer: the conscious, outer brain- the firewall, and the inner subconscious (the lizard brain)- the hard drive. The only way for hypnotism to work is to get to the subconscious by hacking the the conscious part of the brain. One way to do that is by surprise. Surprise leaves a split second gap where the conscious brain tries to make sense of what happened, leaving the subconscious brain open for command. What do I mean by "command?" Well, when you are surprised the subconscious has no controller, so if you call out, "SLEEP" the subconscious in a sense say, "Ok!" You are then under the command of your victim, friend, audience member, etc. I receive a lot of questions in response to this theory, "Can you make me do stuff naughty?" No, I can't the subconscious has the same morals as your conscious brain. Unless you were a harlot, then yes... But I wouldn't do it anyways.
To surprise someone, you have to interrupt a normal everyday thing like a handshake, or lighting a cigarette. For a handshake you can do two things:
1. While shaking his/her hand jolt the arm as not to hurt but to shock and then call out the command ASAP.
2. When he/she reaches to shake your hand quickly lift his/her hand and speak softly and get their focus on his/her hand and slowly talk them down to a sleep mode.
There are also several different ones that sometimes take hours to do. The one I told you is for a quick hypnotism.