Eat pasta (or some other kind of starch filled food) before the race. Starch is a source of immediate energy that can give you, well, energy! Also, always try to eat right and drink lots of water.

FEFreak16 : Since you're fast, I figure you understand the lingo, I'll cut right to it.  You're already doing 6:20s at that pace, which is a good sustained run for a 5k.  The elevation changes are going to make that score shoot all over the place anyway.  Throw a hill in there and you'll lose a good 30 seconds.

To cut two or three whole minutes you'd have to cut a minute per mile, which is tough to find at that distance.  You'd need to run 5:30s to get down three minutes.  You'd have to sub 6:00 just to take off two and some minutes.  

Sprints are where you need to look.  You can do 400 repeats with 20 seconds rest in between.  Do those over and over and over and you'll build the lactate tolerance to run the extra miles.  Overtraining and long mileage won't get you where you need to be.  You need to do more speedwork.  You can even do 800 sprints with a minute in between until you pass out.  That'll knock a little time off.

You're asking a lot.  It takes serious training and extreme discipline with the food you're eating (no sugar whatsoever).  The diet isn't nearly as important as the sprints.

This was my best friend when I was in cross country back in high school. Sand. My hometown had a VERY long river that was completely dry. The river bed was packed full with sand. Not the kind of sand you see in a kids sand box. It was extremely fine sand that was not packed in tight at all. You sink into it about 3 inches just walking in it. When a lot of people on the team seemed to hit a plateau, our coach took us to the river. We spent a couple weeks there. We would run to the river, which would be our mile and a half warm-up. We would stretch, and then run in that sand for 3 miles strait. It will make your calves burn, and your time will be SLOW. But if you can shave about 30-60 seconds of your average sand filled 3 mile run, you will see a significant improvement in your time on an out of the sand 3 mile run.

warmaker :

yes the secret is in the sprint try  practicing running
find an area you can run at your top speed for as long as you can then rest
you heart should feel like its ripping out of your chest

do this repeatedly what this does it build your lung/heart to withstand this kind of abuse
so your body will try to adapt to it. the more you do this the easy it will be to run longer faster witout getting tired 

As someone who did this himself, I will offer you my best advice. First, a little background. In high school, I ran in the 20:00-23:00 range, until my senior year when I finally became motivated (since to that point, running was just a game). In my senior year, I started running 23:00s (I ran about a 23:25 in my first race that year, at the very end of August in a preseason race) and I finished the year running a personal record 17:54 at the state championships.

In order to cut a whole minute/two minutes off your time like I did (I actually cut off 5 1/2 minutes, but the idea is the same), you need to run constantly, and WANT it more than the guy in front of you.

The first step is eating and sleeping right. Prior to that season, I never ate particularly healthy, I was the one guy who went to each practice with junk food and drank soda like it was water. The unhealthy kid who just was sort of there for the hell of it. In my senior year, after an... incident, I stopped drinking soda, and started eating healthy (this was in the middle of the season, so I didn't follow this advice at the beginning of the year). I shouldn't have to tell you what healthy food for a runner is, but eat pasta. Lots of pasta. Especially before races.

The second step is actually doing the running itself. You need to run every day or most every day. You cannot afford too many consecutive days off, and if you are going to take a day off, take Sunday off. You should be running every Monday-Friday, and most Saturdays you should be doing a light jog. Unless your race is on Saturday, then do your light jog on Sunday. Your coach should be giving you a good schedule Monday-Friday, so give the practices 100% and focus on doing what he tells you to do. Make sure you do it right too.

The third step, and possibly the most important, the one most forget, is to develop your core muscles. I was fortunate in that my coach in high school emphasized the core muscle development during the last part of our practices. You should be doing everything in your power to strengthen those muscles, as it really helps to prevent any pain during the race itself, allowing you to push your limits further. It also allows you to run the practices with a better efficiency. Those with well developed cores, tend to finish higher. I had never done core work prior to my senior year. It sucks doing it at first, but it really adds up, and I am grateful for having done it.

And the fourth, and penultimate step is to actually show up on race day and give it 150%. No, not 110%, but 150%. You should be pushing your limits during the race. And you should also get familiar with the course before the race starts. Most coaches take their kids on walk throughs of the course before a race. However, in my experience, most of the runners use this as a chance to socialize. Don't talk to anyone unless they are talking specifically about the course and the race, and a strategy. Focus on anything your coach says, and take everything into account. How hard the ground is, how heavy the air is at that point, and how much pull you can get on a hill. The better your knowledge, the easier it is to take advantage of it. There's something to be said for situational strategy, and being able to formulate a plan on the spot, but there's more to be said for being prepared. Ultimately though, it's up to you, as a runner to perform.

You may also wish, though this is more of a personal benefit, try to seek a sort of balance before the race. I meditate before races, and pull my body and mind together to make sure they are in perfect harmony. Believing in yourself and trusting in your body can really help a lot, though you may have to put up with teasing from people who think what you are doing is strange.

When the race starts though, do not blow your load at the start. If you do, your time will suffer. Example. Regionals and States are held at the same place when I was in high school. At Regionals, I ran about 18:30 (and finished 10th), at States, I ran a 17:54 (and finished 8th). The difference between the two races and a total of (about) 36 seconds? How fast I went at the start. I blew my load in the first mile, and though I had a first mile time of 5:15, my other 2.1 miles were much slower, and 7 people passed me (yeah, I was in about 3rd at the mile mark). In the second race, the States, I hung back with the two top runners on the team (I was the third best runner at the end of the year) and we fed off of each other's energy. We hung together for about 2 miles (our time at the 2 mile mark was something I forget, I was so focused, I never heard, and I never checked later on) and while they pulled ahead, I still had the best race of my career. That small change to my strategy resulted in a 36 second improvement in one race.

I apologize if I got a little personal, and you aren't ok with that, but this is a personal experience that I myself went through, and felt like sharing. I hope it gave you a little insight as to how I managed to do it, and how you may be able to do it*

*legacyme3 admits he may just be a freak of nature. The above is no guarantee that you will be able to replicate his miraculous success.

Sorry for being a little late for replying, but I really like some of your tips. I hope that it can help me out next year. Right now I have track season, so this will be fun.