It takes 16 weeks of hard training (except for the last week) to be ready to run a marathon. And this is for a person who has experience and wants to improve his/her time. Before the 16 weeks you must have a strong base with some experience on speed work. For beginners it may take 6 months of slow build-up before starting your 16 week marathon program. If you are a beginner, speed workouts are not necessary for the first marathon. The goal should be to finish
The marathon is a distance that must be respected. You need to learn to control yourself at the start and at the middle of the race. The middle of the race for me is the 25Km mark. When you get to 25km, hold that feeling. Don't pick up the pace just because you feel good. You will end up paying for it around the 21 mile mark. If you feel good, give it everything over the last 5k
Your long run is the best work out to simulate your marathon race. Run your long run the same way you would like to run your marathon. I don't mean the pace. I mean to run patiently at first, slightly faster in between but controlling the pace and faster in the last 20 minutes of your run
Run your long run on a course similar to the marathon course. Try to do your long run at the same time of day of your next marathon start. During your long run visualize yourself running the race. When you are about to cross the finish line of your long run, visualize yourself crossing the finish line of the marathon and running a perfect personal best
Don't change your eating patterns the night before or morning of your race. Eat what has worked for you before your long runs. Experiment with the quantity of food and times of eating during your build-up. Once you find what works best for you, don't change anything