See also Exercise Basics
Change your exercises frequently
The whole reason you hit the plateau in the first place should make this the easiest change to put in effect.
If you are trying to hit personal bests with some of your exercises then you would want to change them only about every 4 weeks.
If you are not trying to break any records then each week change something around.
See also Suggestions For Workouts
Overuse or plateau?
Sometimes the body not responding is its way of saying it needs a break. Rest and recovery is very important.
The body needs time to recover after a workout.