Dosen't matter just as long as your are relaxed, clear minded and feel that you believe in it otherwise it won't work, also err if you want me to suggest you some then here:
Suggested:
Headphones or Earphones are okay (if the hypnotizm involves your ears, then use earphones)
Position: I think its best if you lay down on your bed without tilting on any sides, just on your back (make sure you feel relaxed and comfortable)
Belief: you must believe it works or it won't take effect at all
Mind power: you might need just a teeny weeny bit of mind power, if you don't know what i mean by it, its technically how you control your mind and how much of your mind you can control, hard to explain really.
That's about it, Goodluck !
Oh my god, before the hypnotism thing, I did a pony test and result was I had the personality of Fluttershy, After the hypnotism (of pinkie pie) I redid the test it seems im more of a pinkie pie now ?!?!?!??!?!