So there you are at the back of the pack. Running a 5k and choking on the dust kicked up as everyone passes you. You start to dream of running faster, not necessarily anything like winning the race, but faster. The nice thing about faster is that it is relative. So 14:55 per mile is faster than 14:56 per mile. Ha ha, technicalities! I’m talking more about significantly faster running. Like 14:30 per mile. The slower you run, the comparatively easier it is to get a little faster.
How do you get faster? Practice! Just kidding. Practice in a way is a big part of it.
There are basically a few ways to start building up your speed. One way is interval training. Basically run faster for a portion of time, then run normal again, repeat. For a 5k, you can run 1/4 to 1/2 mile faster sections followed by 1/10 to 1/4 mile slower sections after a warm up. Your current 5k pace minus 30 seconds to a minute would be a good faster pace.
Hills or weight training is another way to build up some speed. Building the muscles in your legs up give you the power to go faster. Try running up a small hill a few times and walking/jogging back down (1/4 mile length 3-5 times depending on your abilities). Squats are a good power move and so is bike riding to cross train.
Warm up before either of those with a slow jog for 8 minutes and stretch afterwards. Get fast!