Pet control sets the opening
A pet controls the opening seconds of a pull. Those seconds decide where the mob stands and whether the player has room to respond.
Westfall and Deadmines
Westfall and Deadmines have corners, runners, stairs, and small rooms. Send the pet with a target and a position in mind. A pet that runs through the room can add a patrol or pull another pack.
Open ground and caves
Ragefire Chasm, the Barrens, and Wailing Caverns show the same pet-control problem in different terrain. Open ground invites a wide pull. Caves can send the pet through another room. Keep the pet on the target you planned to fight.
Prepare the pet
A prepared pet gives cleaner openers, safer runner kills, and better solo recovery. In a group, make pet setup part of the pull plan.
A pet gives time
Pet control buys time. Use that time to reset, move to open ground, or keep the fight small.
Use the opening
The pet may create an opening. Use it to stabilize the pull instead of taking another one.