You can also use a player to pull when the current target is near death, making sure that the new mob is delivered to the Main Tank when he is ready for it. In this way you can greatly speed up the progress through the trash mobs. This is called Chain Pulling.
Great care should be taken when pulling to avoid Aggro from social mobs, or roamers. One way to do this is to use abilities that are less noticed by surrounding mobs. Body Pulling is a way of inching forward into a mob's Aggro Range in such a way that he notices and comes to you without his nearby friends noticing what is going on. When doing this, the Main Tank should use an ability, such as Taunt, to secure the aggro when or before the mob reaches the rest of the party or raid.