My personal setup is to run Lazyraider and set it so that the other toon is flagged as a tank, thereby setting it as priority for heals. You can also set the toon healing to auto follow the designated tank a certain distance with Lazyraider as well. Then, depending on what combat routine you use, there may be more advanced option to heal your target or focus target. Load it up like this and then run your tank...just make sure to avoid sharp turns or anything that will get your healer stuck.