Velma,
These are good examples. Basically, I find if students feel there is something of benefit in the lesson for them, they'll be more apt to pay attention. And one area nearly all students are always interested in is the profession their training for. To reengage, a story, situation, or past experience that was intersting or unusual usually captures the interest of the class. Once we have their attention, we can bring the lesson back to task.
Barry Westling