Get a car and mark out a half mile, mile, and mile and a half. Make sure you choose a route that is not boring when you mark out the distances. On your first day, try running to the half mile mark and back. Try to do this without taking any walking breaks. Keep running a mile until you can get it in under 7 or 8 minutes. This may take some time. After that, run 2 miles (mile mark and back) Keep doing this until you can get under 18 minutes. After that, keep running the 3 mile run (1.5 and back). Keep lowering your time. My best is 20 minutes and it keeps getting faster.

Don’t run hard 2 days in a row. Try running hard on Monday, Wednesday, and Friday, and take slow, easy jogs on Tuesday and Thursday. On Weekends, maybe try bike rides or something.