Once a link is forged with someone, you may use the link to feed from them at a distance. The deeper and stronger the link, the more efficiently you can draw energy through it. With most such connections, you do not even have to concentrate to draw forth from the person. To a certain extent, you are in constant contact with that person, and while the energy you gain from them passively is only minimal, a number of such connections with various people will help sustain you in times of need as well as prolong the time you can go between more active feedings.
If you choose to actively drain through a link, there are two good ways of doing so.
First, you can simply concentrate on pulling some of that person's energy to you through the link. Center yourself. Focus on your connection to that person, then visualize the person clearly. Visualize yourself reaching out and touching them to feed then breathe in, drawing in energy as well as breath.
You may also extend yourself down through the link, initiating a deeper contact with their energy body as you do so. This is a more direct way of feeding from those you have subtle connections to, and it is also much more obvious to the person on the other end. As before, concentrate upon the person and get a clear image of them in your head. Then focus on extending your subtle senses to that person, much as you would if you chose to see through their eyes or perceive their emotional state.
When you are successfully focused on them, it will seem you are in two places at once. Part of you will be sitting or standing wherever your body is, and you will retain some awareness of these surroundings. Part of you will be focused entirely upon the other person and will feel as if it occupies the same space that they do, or is somehow enveloped around them. Once this has occurred, you may initiate a drain, pulling their energy in through your breath as you had done before.
The target of such a drain is likely to become aware of it at least on a semi-conscious level. They may suddenly find themselves thinking of you for no reason they can explain. They may smell your perfume or catch sight of you out of the corner of their eye. If they are asleep, they may see you enter their dreams. This is a lot like conscious dream-walking. The technique behind it is largely the same. Sensitive targets may actually perceive your presence, seeing you, ghost-like, hovering somewhere nearby.
Of all the things we can do, this has historically frightened people the most. It serves as the basis for all the myths and legends of demonic and vampiric nightly visitations. As such, it is the most revealing of our nature and it will quickly expose you to those it happens to. For this reason, this skill should be exercised cautiously and with great discretion.