These days its much less of a thing than it used to be. Pet AI is a lot smarter in attacking what you want it to attack.
Back in the days pets took full AoE damage so had to be recalled if they were about to go down or were standing in stuff and pets had a habit of getting stuck, not auto attacking or being on the wrong target a lot more than these days.
So basically pet management mostly comes down to (as Vellithe mentioned) being aware of your pet and what it does. Doesn't mean you have to monitor it every single second, but be aware where they are generally is a good idea.
Pet managment also means that choosing your targets wisely is advisable. On a fight with adds you don't want your pets to constantly go back and forth between adds on one side of the room and adds on the next side, try to think like a melee player.
For most easy stuff 2 keybinds will suffice. One being /petattack and the other being /petfollow.
Keep the pet on assist and you'll be fine for 99% of content. If you want a bit more control you can get macros for passive stance and defensive stance as well, but I find that the majority of "casual" content has no real need for that.