Distant healing as taught in Reiki is usually a Reiki II and above technique. Some of my Level I students use the following distant method successfully. I personally use this method often and find it quite effective. I often use it with my Healing Bear.
Using Healing Bear gives me a sense of what is happening during the healing. Bear and I work together often.
To use a Healing Bear or other surrogate, proceed as you would treating a person in a hands-on situation. Perform your opening incantation, calling the healing guides who normally work with you. Take a stuffed animal of suitable size to work with. Say, "this animal represents *******". Concentrate on the stuffed animal representing the person you are sending the healing to. Place your hands covering the conventional hand positions. Using this technique, you should get the same sensations you get while doing a normal hands on treatment.
If you are Reiki Level I you may not care to read more. Most of this information will be quite meaningless to you.
Several of the Level II and higher distance techniques suggest you visualize the person you are sending to. I often send to people I don't know and I have difficulty visualizing. My visualizations are stick figures if I visualize. I don't use photographs as I lose things and often don't have photos available. If I need a focus point, I use the Healing Bear as above.
Another suggested requirement is concentration. I send several healings while driving and feel it best to concentrate on driving. I find, by running the healing in the background, it is extremely intuitive and flowing. I send initially to the person's aura. The symbols being sent and the location adjust without my intervention. I check in every once in a while, just to see what is happening and if the healing is complete. This check in is helpful, especially when sending to someone I work with often. A change in the energy receiving pattern may warn something major occurred requiring further investigation.
I use Healing Bear to send distant healing attunements and to perform distant healing extractions. From the feedback I get, both healing methods are as successful as when performed in person. I prefer doing distant healing attunements and distant healing extractions in real time, at a prearranged time, when the client is prepared. They can work with the process on a conscious level. They also avoid surprises such as feeling an obstruction being removed at an inopportune time.
I never use a part of my body to represent a person I send to; I always use a surrogate or a visualization. I feel the possibility of establishing a tie or connection on the energy level is very real and, from my point of view, undesirable.