Training Tips, from Russ Sears
The goal to training is to teach your body to maximize recovery. Therefore most hard days are followed by an "easy" day, and I would try to sync my body to my training. On the hard days I wanted to feel fresh at the start and on the easy day to feel I needed one, but to be ready for the next hard day.
I generally also wanted to have a 7 day cycle where I completed speed work, tempo work (near race pace or a race), pacing workout (longer speed work) and a long run during the week. And then a 3 week cycle where, the first week I could introduce more or different hard work, and second week get comfortable with it and 3rd week build strength from it.