I am a Senior Citizen and I Don't Know Where to Start
Is there a YMCA or city pool nearby?
If so, this is the place for you to start. It is your best option. Strongly consider going.
1) Join the Silver Sneakers program (YMCA). they offer a multitude of exercise options.
2) Join water aerobics. (best possible option if you have joint, back, or knee issues)
3) take swim class or swim laps.
4) Ask about using an "elliptical machine", they are easy on the knees.
There is no pool nearby?
1) Brisk walk 10-15 minutes a day (knees and joints permitting)
2) Go the website fitnessblender.com. They have a great selection of workouts. Just select from their "low-impact beginner" choices.
3) search online for Tai Chi or yoga programs centered around senior citizens.
How often / How much?
1) Try to exercise 4-6 days a week. This seems to be the magic number.
2) 10-15 minutes a day as a minimum.
3) Be consistent. Don't skip days. Consistency is very important. So pick a program you will continue