Run two separate speed workouts consisting of 200 and 400m repeats. Gordon Sleivert, now vice president of human performance for the Canadian Sports Centre Pacific, discovered that 400m times help predict mile race times. Before you launch into anaerobic speed sessions, warm up with 15 minutes of easy jogging and then stretch. Jog for another five minutes. Always cool down and stretch after a speed session.
Run 200m intervals. Condition your body to run anaerobically and your muscles to react explosively with hard running; “hard” means a pace slightly faster than your current 400m pace, not an all-out sprint. If you run 400m in 80 seconds, then you should run 200m intervals in 38 seconds. Follow each 200 with a two-minute jog. Depending on your fitness level, repeat the intervals six to 10 times. As you adapt, reduce the recovery jog to 30 seconds.
Run 400m intervals. Warm up and focus on speed. Run the first 200m five seconds slower than the second 200m and run the second half faster than your mile goal pace. On a different day, add a twist and focus on specificity instead. If you hope to run the mile in six minutes, then your 400m splits even out to 90 seconds per lap. For this workout, run your 400m repeats in exactly 90 seconds and gradually reduce the recovery time from two minutes to 30 seconds between repeats.
Practice running uphill and downhill once a week. You gain explosive power surging uphill and you improve speed and stride rate flying down. After 30 minutes of jogging, choose a steep hill (about 100m) to run up and surge at a pace that feels like race pace. Jog to the bottom and repeat six to 10 times. Follow the same procedure for downhill running, but choose a gentler descent . Don't risk injury by losing control running downhill.
Increase muscle strength. Advance leg speed by strengthening the muscles needed most in the mile: calves, quads, glutes and hamstrings. Integrate strength work into your daily routine at least twice a week.
Flex your muscles. Stride rate and stride length determine leg speed. Tight muscles prevent you from opening your stride and gliding. After warming up for 15 minutes, stretch your hamstrings, glutes, calves, groin area, hips and quads, and hold each stretch for 30 seconds. Stretch your muscles again after your workout. Muscles stiffen and tighten during intense training sessions.
Build a solid base. Before you train to run a fast mile, run an easy to moderate pace for at least 12 weeks. The stronger your base, the better your body adapts to more intensive training loads.
Mix it up with VO2 Max workouts. Enhance your running economy, which is critical for clocking a fast mile, with three- to six-mile repeats at 5K race pace, or 30 to 40 seconds slower than your maximum mile time. Recover with a four-minute jog, and gradually decrease the recovery time to 45 seconds.
Improve lactate threshold with three to four 10-minute intervals at a pace 40 to 50 seconds slower per mile than your one mile tempo. Advancing your lactate threshold improves running efficiency, endurance and economy. Most of it all, it brings you one stride closer to reaching your goal mile time.
Wear running shoes suitable for a 5K when running speed workouts. Start speed workouts conservatively. The goal is to run faster toward the end, not at the beginning.
source: Bridget Montgomery
Try this to build more stamina http://youtu.be/BoBP73d2El0 there are also articles online to help your stride. Increasing your stride will definitely help your mile time