Here's a great article about running and suggestions on how to improve your times by running smarter.
by Stephen M. Pribut, D.P.M.
Director, Executive Board AAPSM 2002
Bill Bowerman, in his coaching days at the University of Oregon, would say "Run Tall". This sums up the style of many of the recent and current greats in long distance running. You should run standing up fairly straight, not leaning forward, twisted to one side, or tilting backwards. You should be looking ahead at where you are going, not staring at your feet or the ground. Of course on a trail run, you might be checking out the ground and what is coming up next, if you value your ankles.
Starting with the foot: Where should you contact
Some say to run on the ball of your foot, others say contact the ground with the heel. I take a middle of the road approach. Studies have shown that good long distance runners usually contact with the midfoot. Slower runners contact between the midfoot and the heel, faster runners a bit further forward. Only sprinters or short to middle distance runners should contact the ground with their forefoot or the ball of the foot. While there may be exceptions to the rule, this is a good way for most beginning and intermediate runners to start out. It allows for better shock absorption, less stress on the calf muscle and Achilles tendon, and better rolling forward onto the next stride. Your muscles will then be used in a manner that is similar to how you walk, and this is the pattern of muscle firing and contact pattern which the muscles are accustomed to.
Hips & Head
This part is hard to think about: Where are your hips when your foot hits the ground. Some people have suggested that your foot should be under the center of gravity of your body when it strikes the ground. A line from your head through your hips should end up at your foot. Keep the head fairly straight and look ahead. Turns to the side should be done carefully and usually mostly from the neck up to avoid twisting your body and making you unstable in your forward progression.
This is what you use when you haven't obtained a jogging baby stroller. Actually, it is where you allow your arms to swing. First, and most importantly, don't tense up and carry them stiffly with your hands balled up into a fist and your elbows completely bent. Relax. Carry your arms at your side somewhere between your waist and your chest. Make sure they are not too high or too low. One arm swings forward while the other one goes backwards. This occurs opposite to the foot and leg motion. Sprinters on the track move their arms in a straight forward-backward motion. Most longer distance runners use a slight arc as they swing their arms, but the better ones don't waste motion by moving too much from side-to-side. In other words, they don't swing their arms excessively in front of their body.
The knees do not have to come up very high for long distance runners. Only sprinters or those of us chugging up a hill have to left our legs high.
One of the biggest problems of form in long distance running is overstriding. Make sure that you don't do this, it can lead to a host of problems including Achilles tendonitis, ITB pain, and iliopsoas muscle pain.
While some like to tell you how to count your breathing in seconds both in and out, we will just tell you to keep breathing, deep and regular. In most cases your breathing will take care of itself, as you run faster, you'll breathe faster. And yes, most runners are mouth breathers or at least nose and mouth breathers. It would be impossible to take in adequate oxygen just breathing through your nose.
Uphills and Downhills
Slow up a bit on the uphills. In general it is a bad idea to try going faster. Move your arms a bit more to help you imagine that you are cranking your way or pulling yourself up hill. Shorten your stride and chug on up. You can think of the little train that could and repeat "I think I can" on the way up a big hill.
On the downhill, be careful. Go slow. The biggest risk, is to your knees. Your quadriceps do the bulk of the braking and be overworked without you being aware of it. If you are racing, then you may lean forward a bit and fly down the hill in a short race, but certainly be more careful in training. In fact many runners who use hills as part of their training will walk down the hill while recovering to run up the hill once more. This is a good way to rest and recover while avoiding the excessive knee stress that downhill running can cause.