To get faster, it is very important to do one, two, or three runs at faster pace during the week. Always drink water even if you are not thirsty. Take rest days the day after your long runs and the day before your hardest speed workout.
Diversity is the key to successful training, and makes running more exciting and less boring.
Train at different paces, which in my opinion, is one successful ingredients of Kenyan training programs. Running hills is very helpful, especially at the beginning of the season. Have 1-4 months per year where you run only leasurely.