First of all, I ran 7 miles today! The farthest I have ever run! I have run 6 miles many times, but until today, that was it. My current training plan is to run 4-5 miles 3 days a week and one day each week run a long run, adding one mile to the distance each week until the week before the half marathon. I ran the first 5 miles today without taking any walk breaks, but then at mile 5 and mile 6 I walked for about one minute. Next week when I run my long run, I plan to try this routine: run 8 minutes, walk 1 minute. This run/walk method has been made popular by Jeff Galloway, and I think it will be good for me and my knees.
I have two friends who are beginning to run. For them and anyone else out there who is interested, here are a few websites with helpful information.
Beginning Runner's Guide
Hal Higdon's Beginning 5K Training Guide
My advice is to take it slowly, run slowly, and increase your distance/time slowly. I first began running consistently 18 months ago, and most of that was with the double stroller. Commit to sticking with it for 8 weeks before you decide that running isn't for you. I promise you, you will be hooked! Remember, each mile burns about 100 calories! (That's walking or running).
One more thing, once you are committed to running regularly, invest in a good pair of running shoes and some decent running socks (not thick 100% cotton ones).