A pre-talk is simply a brief talk about what hypnosis is, addressing any fears or concerns the client may have. There is no need for a 30 minute-lecture on the nature and history of hypnosis. 30 seconds is normally plenty of time.
Given the common misconceptions, you will need to address some of the rumors and myths about hypnosis and explain the truth to the person. Of course, doing this is a great way to drop in expectations and increase expectancy. E.g. "When you feel that wave of relaxation and go into trance."
Normally, you would let them know they are not asleep during hypnosis, they will still be able to hear you speaking to them in, they will remain in control, etc. I would always let them know that they will not be made to do against their moral or ethics, or that makes them feel uncomfortable, because the whole idea is that they are going to relax and enjoy it.
[An Example Pre-Talk: ]
Is there anywhere in your memory, or your imagination, that's a special place to you? Somewhere that just thinking about produces feelings of relaxation, calm, peace, safety, serenity...
Excellent. What I'd like you to do is take four deep breaths and on any of those four breaths you can let your eyes close and imagine yourself in that special place, seeing those sights that calm you, hearing those tranquil sounds and feeling that sensation of deep relaxation. Okay?
[Wait for Client to close their eyes] ...That's it. Down into that place of deep peace and serenity. Down deeper into relaxation... And we all have times like this, where we feel so relaxed and at peace that our brain kinda just zones out. And that is something that we hypnotists call 'trance' - and this is what hypnosis feels like.
Some people think that you become a zombie, or just zonk-out completely, but it's not like that. What you'll experience is more like the first few minutes when you wake up in the morning and you're just floating in that hazy space between being not quite awake but not really asleep. Or, like when you day-dream and your mind just drits off to some other place. You're still safe and in control and could snap yourself out of it any time you chose to. (But the truth is that you're normally so relaxed that you just don't want to!) Or, those times you have when you're driving on a familiar route and your conscious kinda takes a back seat. And when you get home, you're left thinking, "how did I get here?!"
You know exactly what I mean. Trance feels just like what you're feeling now, as you enjoy that special place. And any time you hear me talk about 'trance' you'll know that it's really just a hypnotic code word for relaxing down into your special place and enjoying those feelings of peace and tranquility and deep, deep relaxation, as your conscious mind takes a nap and your subconscious opens up to suggestions and your imagination is given free reign.
So, when you're ready, you can open your eyes, feeling fresh and alert and raring to go...