This is an old Runner's World page already (it dates from 2007), but there's still a lot of good advice by Jack Daniels on it, like balancing easy and hard running (80 and 20 percent of weekly mileage respectively) and how long your long runs should be.
Photo by Josh Biggs, taken from Runfaster5k.com
You can find the ten principles 'from a renowned coach [to] help you tailor-make the smartest training schedule' at Runner's World.