Read Arthur Lydiard...
They have several good posts right here in front of the Main Forum.
The basics in a nutshell are:
The long run puts the tiger in the tank. However you probably need to build this up to over 2 hours in length. That might take you a few years.
Always do at least one speed development workout per week. Perhaps the best way to learn that is to talk to a top sprint coach, but TRUE speed development is very short sprints. 10 x 200 is speed endurance at best, but likely hard interval training for most.
Avoid Hard Interval Training. Yes, it is important, but must be done at the right time and in the right way. This is why many fail to become good distance runners.
Avoid Racing too much. This is similar to the Hard Interval Training.
Beware of Tempo runs too. You must do these things but mileage/base building/Aerobic ability must be developed first.
Read Arthur Lydiard