This is my short technique that I call the Golden Tendril.
This technique may be of use to psi vampires but anyone can use it really. Myself, I only use it sometimes to get a boost, or 'buzz'.
The technique:
Place your fingers in an arrow shape pointing at the person to take energy from. Now, visualize a golden tendril going from your aura/subtle body. It does not have to be golden, but this is how I always see mine. Visualize and will it to extend to the donor's subtle body. The fingers are merely directing your focus.
Attack until the tendril pierces. Make it become hollow and will the energy out of their body through the tendril to yours in a stream of energy, literally like a stream of pure golden energy. Withdraw your tendril.
Warning: Their aura/subtle body will heal itself over time and therefore you will need a strong will. Some people such as Psions know psychic shielding so this method may be rather more difficult or impossible on them.