If you haven't, you're lucky. If you have had the pleasure of dealing with these individuals, you've already developed some skills in this area. This list will give you some additional strategies to try if the situation should repeat itself. Have shorter breaks more often.
Long breaks encourage wandering away, phone calls, etc.
Learner curiosity will have them back on time. This allows stragglers to join a group and not feel lost if they are a few minutes late. Use small group discussions that promote involvement by all participants. Provide storage for extra items like newspapers and books. Ask them to write a to-do list to empty their mind, and then put it aside until after class.