In DEP For Marine Corps, wants to get better at running?

Just ran my IST this past saturday, got 109 crunches, 15 pullups and a 10:55min 1 1/2 mile. for how much i work out and run about 4 times a weeks for at least 2 miles each time my run seems to not get any better. Anyone have a good run workout plan that i can do that involves effort level and time intervals. All i have is a stop watch and 32 miles of neighborhood to run around. (Please no distances please i dont have that many distances mapped out) My goal is to work up to a 3 mile run i can do in 21:00 for the Marine Corps. THANKS