In reply to thelostjockey:
Mix long runs with some dedicated track sessions.
Find a decent running track. Might sound boring but practice at your race pace or faster. Easy to bail out if you start to feel an injury or tiredness, nothing worse than being five miles from home and crocked. Get to know what your desired pace feels like. Have liquid at the side of the track, so you can experiment with hydration , no need to carry any. Also on a track you should know the precise distance, I saw a lot of exaggerated training run pace claimed, that couldn't be reproduce in a race.
Get someone to join you, share the training load. I knew someone who trained solely on a track as miles on the road caused foot problems, he was well under three hours for his first marathon, I regularly joined him for his track sessions.
John