Mile repeats are a great for getting two important aspects of running stronger - endurance and speed. One mile is long enough to have you improve on endurance yet short enough to allow you run very quickly and have rapid foot speed.
Mile repeats are just what they sound like - running one mile multiple times with a short break in between. It is best to have some rest time between each interval. While you may be tempted to sit or stand around, it is best that you keep moving. It is recommended that for every mile you perform at a high level, you follow it up by slowly jogging half a mile. This way you have enough time to rest yet keep your body active and prepared for the next interval.
Of course, warming up and cooling down are important parts too. For your warm up, run about two miles at a comfortable pace. If you wish, you can stretch after one mile. However, as long as you stretch beforehand, you will be alright. As for your cool down, limit this to a maximum of two miles. The purpose of your cool down is to calm your body and release extra tension. Therefore, don't overwork during this time.
Another important aspect of mile repeats is how many to do. This will ultimately depend on your speed. Your speed should be quick, but not as fast as a race pace. Therefore, only four to six should be performed. This is because the purpose of this workout is to get both speed and endurance built up. If you perform less than four, this workout will be dominantly for speed purposes and you could have held back, going for more repetitions. If you went more than six mile repeats, you could have sped up and taken some endurance away.
When doing these repeats, stay in the inside lane if running on a track. However, it is best to switch directions on occasion so you don't overwork one leg. If you are running on the roads, be sure you avoid streetlights or other areas that will force you to stop.
A day after this workout, it is imperative that you go on a slow, easy run. This will allow your muscles to relax and get more out of the workout before. Therefore, only consider running for one hour at the highest at a slow, easy pace.