If you are a disciplined person, protection from psychic vampires is easy to achieve: just ignore them.
Psychic vampires in general are good at pushing the buttons of others, finding and exploiting their weaknesses. Most vampires operate on the emotional level, and if they don't find any weaknesses they lose interest and wander away. Usually such people are stuck in their own emotional mud, and even if they are trying to be nice, their presence is uncomfortable and irritating. The feeling of need that they radiate can be overwhelming.
Simply ignoring these persons and letting them play their dramas on their own is generally the best and efficient defense. If they find your buttons and enjoy pushing them, you have to become aware of these weaknesses within yourself and change - blaming them or struggling against them doesn't work. Focus on following your own path and let them find someone else willing to play their dramas.
Sometimes the psychic vampire is a loved one you feel responsible for, and in this case ignoring them is not a good solution. The first step is communication; explain to him or her the results of such actions. If that doesn't work, you can either go back to maintaining a neutral attitude, or you can force awareness into them by acting as a mirror. Acting as a mirror is not pleasant, but it also puts pressure on them - they will either change or avoid you for miles away.
The thing to remember is: you can't go wrong with self-discipline for protection.