I did some walking for 15 minutes today...yay

I actually followed an exercise plan by actually doing some exercise today.  I did some walking for around 15 minutes and burned nearly 200 calories.  Though my form was bad, I am happy to have done exercise. Now if only I have a plan, at least a set plan to exercise.  How often should I exercise?  What time should I start to exercise?  How many times should I exercise per day and for how long?  Those are things that I need to consider.  Back to the subject of the exercise I actually did, I feel great today, if even a little sore.