Tell your doctor about any new exercise plan 

Read The Art of Exercise about preparing for exercise

If you create your own plan (eg Squat jumps, running on the spot)

 Unfit? Make sure you do 15 seconds 8 out of 10 and 45 seconds rest x 10 

Not too bad? 30 seconds 8 out of 10 and 30 seconds rest x 10

Fit? 45 seconds 8 oout 10 and 15 seconds rest x 10