The importent thing to keep in mined is intent. You must, from the very beginning, know what you are about to attempt. It also depends on what kind of work you are doing. If it is Reiki, you should have little personal input/output of energy. This being due to the energy not being "yours". However, in any energy work you can simply ask that the person before you receive the healing energy you are offering and nothing else.
As a more useful answer you can imagine a shield of pure white light surround you before starting the session.
Hope that helps.