First and foremost, you must decide for yourself why it is you would like to start running. Health, weight loss, or perhaps to fit in those jeans that you stored away in the hopes of fitting into them one day. Write it down - your goal that is, make it known, and put it in present time so you can see it and visualize it every day.
Another thing I found very useful is to create a schedule and follow it. It is proven that if you write things down in a calendar, you are more likely to follow through on it. Not only should you write down what days you are going to run, but you should also take into consideration the distance (or time) that you are going to run on that particular day.I have done this for many years and it has proven effective for me. Of course those days that you just feel like going for a run or that a run is necessary to melt the stress of the day, then lace it up. There is no harm in adding an additional run during the week - just don't overdo it.
Start your run slow and listen to your body, there are a lot of running aids and guides to help you when you first hit the pavement but running is not really a science. Run at your own pace, stop to walk when you have to, and don't feel like you have to beat anyone other than yourself.