It depends on a person's set up. I have more than one monitor on my desk. After launching my three accounts, I put my two followers screens in the smaller monitor and have the leader's account on my larger one. I play in "full-screen windowed" mode, making it easy to go from one screen to the other.

I also make sure to have "target assist" checked so when the followers are targeted on the leader, they will attack anything that the leader attacks.