When you check the rack what exactly do you look for? I'm talking more in 9 ball here. I know you want at least the first 3 balls touching, but is there anything else that is as important? I know to check if the racker is tilting the rack to one side or the other, but is there anything else to watch out for? I've never truly studied how to rack so I've always just checked to make sure the first 3 were touching.