Keep it simple, that is one way to be sure you are progressing in maintaining your body.
Here are 3 moves, basic but beneficial.
Practice these at your ability and then work up to get more out of them.
Squat- no weights needed. Just squat as low as you can, trying to keep your feet flat on the floor or ground. tips- extend you arms if you have trouble with balance. Hold on to a chair, table, or whatever for stability to start. Stand on slightly angled ground to help with balance as well. You should after a time be able to get lower and more steady. This is a simple but effective move for legs, back and overall tone.
Push up= we all know how to do these correctly, or do we?
Arms directly under shoulders, elbows back, push down not out.
Go all the way down flat, not stomach or chest first. Push up slowly. Breathe!
For more challenge, put one leg on the other crossing the ankles. Do one good one if that is all you are able. Aim for 20-25 repetitions.
That's it for now.
Just these two moves when done correctly and often can be very helpful for overall fitness.