You can’t go wrong with a gradual build; after almost a year of not exercising I started the same way. Pick something simple (and make sure you have time to do it) and do it every day, no excuses. I found making sure I kept my focus the first two weeks to be very important (habit building I guess). After that start adding either time or effort to your sessions, if you start to hit a wall try dividing your sessions and doing “two-a-days” using the same building principal. If you find yourself with a less than positive mindset after a few months try mixing up days with different workouts (also good for your total body health so I’ve been told) to keep things fresh. For walking specifically, I’ve found a variety of outdoor routes keeps me from getting too bored. As to what else to do, biking, light weight lifting, jogging, and light military sets (push-ups, crunches, pull-ups, jumping jacks) should be doable early on, as long as you keep to your gradual approach. Oh and don’t forget, as you begin to work out more and more, keep a balanced diet with plenty of hydration and a maybe add some extra protein to keep the muscles healthy.