Start moving! Anything is better than nothing. If you haven’t exercised in awhile you can start by taking the stairs, walking to run an errand, parking on the other side of the parking lot, etc.
If you are a women and weight training, make sure your weight is appropriate. You want to build muscle not just endurance. You should be fatiguing anywhere between 8-12 reps. A few sessions with a trainer may be needed to make sure your weight is appropriate.
Balance training is a critical portion of your workout. It will help improve posture as well as minimize your risk of falling.
Only eat when hungry and never stuff yourself. If you feel too full your body has consumed more calories than it needs. One indicator is once the food doesn’t taste as good. Your body is sending the signal that you have had enough!