I found a great article from Running Times on building a good base early in the year. Courtesy of An Ultra Runner's Blog Click here for the full article.......this is just a bit of the article.
But remember the fundamental insight, Arthur Lydiard's great contribution, that distance running is an aerobic sport and that the best way to build aerobic strength is through steady, aerobic running, not by racing, blasting 200s, or grinding out race-pace kilometers. "Just keep building those aerobic enzymes, year after year after year," Culpepper says. "You have to put in a good solid block of just training, where you're not racing, where you're not running workouts, where you're just running a lot and your body is getting used to running a lot and recovering. That comes from running long runs and running good mileage -- week after week after week."
"Running is a continuum," Kennedy says. "It builds on itself. And it doesn't build on itself just from the beginning of the season to the end of the season, it builds on itself over years. The reality is, the more you can do, the better you will be. Within reason -- there's the balance of injury and illness and overtraining, and that kind of stuff. But up to that point, the more you can do, the better you can be."