My suggestion is quite simple; study everything you can find when it comes to the psychological principles of magic/mentalism which happens to include how to use your words, body language, etc. in order to plant the seeds you need to plant; Banacheck mentions this is book one of the Psychological Subtleties series and I do believe several others have echoed it over the years, including Kenton Knepper who, along with his team-mates, have done more in this area than just about anyone (attaching strong NLP associations at the same time)
Understanding statistics is another area you will want to look at; the easiest and most practical tool on this point that's Magic related would be the book TRADECRAFT. Though it's about cold reading it has an amazing appendix of statistical commons.
PRACTICE is really the only way to learn this. You might want to pick-up a copy of Michael Murry's "Between the Lines" in that it exploits this line of thinking at a significant level; it's one of my favorites bits of business. Another routine that I use a great deal is MAO TOU KNOWS by Stuart Palm, it's a phenomenally powerful Pendulum act and that's before you start doing anything with the pendulum itself.
Best of luck!