It's quite easy to become a psychic vampire: be needy, confused, stressed, irritable and oblivious to who you are or what you want. If you reduce yourself to such a base level, primal insticts take over a large part of your consciousness. Feeling a hunger for psychic energies and attention may become dominant and by reacting reflexively to it one can quickly deteriorate to being a psychic vampire.
While becoming a psychic vampire is generally not something a psychic should aspire to, learning about and even practicing some techniques of psychic vampirism can be beneficial.
Full-on psychic vampires are created subconsciously, from a deep need they are unable to resolve. So they just fall into a destructive behavioral pattern and get stuck there. Unfortunately, it's like quicksand: the more they struggle the faster they get drawn in.
For a psychic studying vampirism techniques the basic idea is the giving and taking of psychic energies - it's about balanced exchange. If you engage a psychic vampire who doesn't respond to reason and just takes and takes without any regard, there are two possible ways to deal with the situation: either give more than they are willing to accept (overload) or take more than they are willing to give (bleed dry).
If you chose the second solution you are basically using their own medicine against them. If you are not careful and have some hidden needs of your own, you might lose this battle and get dragged down to their vibrational energies - and temporarily become a psychic vampire yourself.
Be candid with yourself and make sure not to enter losing battles.