Let pile pur collecctive experiences here.
For a hunter in an instance, pet should be on passive at all times. If you BM watch that your pet is not pulling the aggro away form the MT.
If a trap is not need for the initial pull drop a freeze or freezing trap to the back so the healer can run to it if it gets aggro. Also seeign the big as white spot alerts people that healer needs help. Also can be used by the clothie DPS.
If you pull aggro be careful when feigning becasue if mob goes to healer group is f@#$%^d.
Don't forget Misderction to bring aggro back to tank, careful you do not MD a shot towards a caster ( i di dthat to Probenzo once lol) by accident.
Some threads I have read tells you to have maxed out Shadow protection to minimize your pet getting feared.
Remember pets now attack form the back so it is possible fo rpet to wander too close to other mobs, so watch the pet.
Other hunters please add more comments or questions to this