[Harper]

It's pretty universal as an idea, don't play with anything you don't understand, would you go into a nuclear power plant and start pressing all the buttons?

Basically I can understand an urge to try this method because at the moment you are curious and only kinda half believe, take the advice of the others and simply reject your curiousity if only because they do 'work' but not in your interest, the people you are speaking to don't know anymore than you and all they want is a chance to come back into the physical and will do as much or as little as is needed to achieve their end. Especially at this time there is a big bottleneck in the deadzone and the nasty ones are real keen to get back, because its nicer in the physical (although you can evolve spiritually in the deadzone also but its easier if you are in the physical)

However your question is quite clearly different, I guess you would really have to ask a medium how they prepare, I can only assume that their unique abilities allow them to be more decerning with time, but I suppose they will have had their bad experiences too.

A true channell is a whole different ball o wax and must prepare physically as they can get great physical damage, such as burns etc.... if they are not properly trained. There are way fewer people channelling universal information than claim to be, it is indeed a very complex thing and not something that just happens to you.

From personal experience I think an unflinching acknowledgment that you are in control is necessary, you can't just believe this though, you must trully KNOW it and you can protect yourself, however you must not falter and that is not easy.