Walk before you run.
How to avoid a few common running injuries.
I see it all the time. People want to start running as a cost and time effective way to get in shape, and it is just that, but there are a few things you should know before just starting up.
Even light jogging causes little stress fractures in your bones. This is ok! It's the same way lifting weights tears muscle down in order to rebuild it stronger. Give yourself a rest day between runs for your bones, ligaments, and tendons to recover, not just your muscles.
A 20 minute walk/run is going to be a lot harder on you if you aren't already doing regular 20 minute brisk walks. Unlike running, brisk walks can and should be done daily. Once you can walk quickly for 20 minutes, you're ready to start adding short runs in as you alternate walk/run/walk/run/walk.
Focus on smooth, not fast! Speed will come out of repetition, but form takes focus. To minimize jarring and physical wear and tear, try to focus on keeping your shoulders gliding forward rather than bouncing up and down. I always envision the moving sidewalk at the airport. To accomplish this you may need to shorten your stride, and possible bend your knees a little more. It may feel funny, but once you can run smoothly, you'll progress a lot quicker, and hopefully safer too.
Stretch after walks, stretch after runs, stretch after workouts, stretch at work.