The key to running faster is disciplined practice and training. There are three basic forms of running training. The first is regular long-distance running to boost your endurance. The second form is called fartlek running and the third is interval training. The three forms of training are further explained below.
This is just like jogging. The goal is to run at 60% of your maximum speed, and maintain the same speed for as long as you run. Always set a distance before starting your run and follow through to the end no matter how much you begin to struggle throughout the run.
Therefore, I recommend you do not set ambitious goals for distance of time when you start out. Start at a distance you believe you can achieve and as you build up endurance and strength slowly set higher goals. This form of running is purely to increase leg muscle endurance.
A set of structured runs with breaks. Once you have warmed up, start by doing sprints at 80% of your maximum speed, with 1-2 minute breaks in between. As a beginner I would suggest 5 sets of 400m with 2-minute breaks between runs. In these breaks stretch your legs and take a small sip of water, as each run will drain a large amount of your energy.
Similar to fartlek running, but with a much higher intensity. Interval training is based on doing sprints of 90-100% of your energy, with breaks in between. This means that when you do your run, you give every last ounce of energy at every time to achieve the fastest speed. This form of training will find you unable to breathe, walk or think once you have finished, as you will be so drained your body will be starving for nourishment and rest.
Start with 6 sets of 200m sprints as a beginner, with 1 minute breaks in between sets. Important to remember with this form of training is that you will need to conduct a recovery sessions the following day. This means you will need to do a slow jog, and stretching the next day as your muscles will be so contracted and have a large amount of amino acids built up in them from the interval training session.
Finally, it always helps to visit the gym and build your leg muscles. High repetition, low resistance (light weights lifted many times) training will boost your endurance, while high intensity low repetition (heavy weights lifted fewer times) will build your muscle strength. With muscle strength you will be able to run faster short distance impulse sprints, while endurance guarantees a longer and more stable run.