When I started running, I used a run/walk system--I can't remember where I got it. Search on Runnersworld.com for a run/walk chart. Or google Hal Higdon, it might have been his, come to think of it.

Anyway, you're on the road for 30 min. Run 1 min., walk 1, repeat for 30 min. After a week you move to run 2, walk 1 for 30 min. A couple of weeks take bigger time jumps--I think after you get to 6 mins., but you never walk more than 60 secs. It is very gentle and I really enjoyed it.

I found on Runners world that walking for 60 seconds after each mile of a marathon helps you keep going and not get too tired. It tried it on the one and only 5K that I ran and I finished with an excellent time for me--and I hadn't run more than 2 miles all year!