The first principle that I would recommend to you is to choose the psychic, not the tool. What I mean is , having of course first decided what general category of work you are interested in (psychic reading, bodywork, hypnotherapy, etc.), look for someone you feel drawn to and comfortable with. This doesn't mean that the work you do with this person may not push your emotional buttons - that often happens when we're on our cutting edge. But if you feel uncomfortable just being around this person your intuition is telling you that this is not right for you at this time. On the other hand, if you do feel drawn to someone, or even just to their advertisement or flyer, it doesn't really matter a lot whether they're reading tarot cards or palms, doing astrology, channeling or clairvoyant readings. Trust your gut, and go to it with an open but discriminating attitude.
The second principle is that you are always in charge of your own session. Metaphysical workers are as human as anybody else and they will relate to some people and some issues better than others. If what you are receiving doesn't feel right to you (not necessarily comfortable or easy but right), then realize that this may be perfectly good stuff for someone else but not for you.
This applies even to messages from channeled entities. You are in charge. If the information you are getting is interesting, stimulating and makes sense to you on some level, then what difference does it make where the information really comes from? And if a channeled entity tells you something that feels wrong to you, always trust your inner guidance before all else.
Every spiritual master has taught that the direction to the Highest is within. We humans need each other to do our healing work, and if you're human you're doing healing work. However, we need to stand in our own power with each other. Only you can choose what you believe. Even if you have given that power over to someone or something else, still it was you that gave it, and only you can reclaim it. In fact, just acknowledging your freedom to believe whatever you wish, and to experience the results of that belief in your life, immediately puts you back in charge of yourself, standing in your own real, exquisite and immense personal power! So, as always, take what you can use and leave the rest.