How old are you? The older you are the slower you need to start. The biggest problem being that you're already fit so your cardiovascular system can support a higher level of intensity and duration than the muscles and ligaments in your legs can support.

The best program I've seen is on slowtwitch from BarryP (http://forum.slowtwitch.com/gforum.c...ogram;#3920587).

Basically you run 6 days a week - 3 short, 2 med and 1 long run per week. Med and long runs are twice and three times as long as short runs respectively. Start with your short run 10-20 min and increase total time no more than 10%/week. It doesn't take long to get your total time up to a reasonable amount. Once you've done base training for a while he has suggestions for increasing speed.

When I was in my 30's and 40's I could just start running from a period of inactivity and I wouldn't have any problems. In my 50's I have to follow slow start plans as I outlined above.