Body pulling is a method of pulling that relies on walking into a mob's aggro radius, instead of the most common one by damaging it with a ranged attack. The method leads to the mob noticing you and comes running for you (or starts firing or casting from a range if it has ranged attacks).
An advantage to body pulling is that the range at which mobs detect damage tends to be slightly larger than the range at which they will simply run along with a friendly mob to see what the fuss is about. As such, it is possible to separate some groups with body pulls where any form of damage-based pulling would pull the entire group.
One difficulty with executing such body pulls is that it takes a while for mobs to react to you being in their aggro range. If you just keep walking ahead until something happens, chances are that you have actually placed yourself in the aggro range of yet another mob (an "add") which will trigger shortly after you notice the first one coming for you.
Players attempting a tricky pull with body pulling will commonly take a few quick steps ahead and then retreat and watch for a reaction. If there was no reaction, the procedure is repeated, only slightly farther ahead than the previous time. This takes good reactions, eye-hand coordination, and perhaps most of all patience. It will be quicker once you know the aggro range of a given type of mob of a given level, which is where the experience comes in.