There are three basic types of runs: over-distance, speed, and tempo. Over-distance is just what it sounds like, long runs that build up your endurance. Speed workouts usually involve repeated quick intervals of short distances. Tempo runs are usually mid-distance runs that include lengthy stretches at a fast pace. Right now I would say that your key is to build your distance base with longer runs (probably 60% of your runs should be over-distance, 30% should be tempo, and 10% speed). Go ahead and add a mile to your long runs and then keep adding another mile every two weeks or so. That way you will build up gradually to the point where ten miles is just another long run. For the tempo runs you may want to try something like a five mile run where miles 3 and 4 are run at what you hope to be your race pace (miles 1,2, and 5 should be run at faster than warm-up/cool-down speed, but where you still feel relaxed). After the tempo run you may want to run a few strides (sprints of about 100 meters where you work on quick turnover and form; do not go all out). For your speed work, I would suggest doing repeated 1 mile runs with a very slow quarter mile jog between each one. You want these to be fast, but not so fast that you can't run the later intervals at the same speed you ran the first ones (if anything, your times should get faster towards the end of the workout, not slower). I would start with three mile repeats for the first couple of times and then try and work your way up to the point where you can do five. For the first couple of months you'll probably only want to do a couple of speed workouts each month, but as the race gets closer you may want to bump that up to once a week. Let us know how things go and if you have any further questions.
Good luck!
Jay
