I've found an easy way to 70 mpw is to run 10 miles a day, with an easy way of doing it by running 2.5 as a warm-up/steady, 5 hard, and 2.5 steady/slow. (or 2 warmup, 6 hard, 2 cool down)
That's 10 miles for the day in a solid 60-80 minutes. Everyone has 60-80 mins a day. A normal yoga class is 75 mins.
Now obviously this method won't produce the fastest times, but it will get your mileage up and make you able to run a solid half or a decent full.