Here's my advice for all the would be runners, who are about to jump in the running bandwagon. All of these tips emanate from research and experience:
Practice - You can't just join a run without preparation. It's like driving your car at a drag race without even tuning up the engine. You don't want break down along the way, so proper conditioning is the key. Start practicing a month away from the event. Gradually pace and push yourself. For me, it's still better to practice outdoors than on a treadmill where you're running but aint going nowhere. You need to be acclimated with nature's elements.
Watch your breathing - Your breathing rate changes when you're running, and you want to pump in more oxygen in your lungs than usual. Breathe in within 3 steps, and breathe out within 3 steps. Intervals would still depend on the length of your stride, though.
Posture - Good posture must be maintained throughout the run. Otherwise, you would feel the soreness on your shoulders. Avoid leaning forward because it might affect your sense of balance. Straighten your posture, but stay relaxed.
Swinging of arms - While running is mostly about lower extremities, the motion of your upper body will ensure your stability. When you run, the natural movement of your arms should be forward and backward, not across your chest. This will cause unnecessary waste of effort and energy, since it is not really contributing anything. You're not gonna knock down people along the way, so don't clench your fists as if you're ready to punch someone. Just loosen up.
Lift your legs higher - Try to lift your legs more as you stride. Power should come from the legs, not your heels. If you don't raise them high enough, you will put a lot of stress on both your feet as a bulk of your weight comes crashing down every step. But remember, it's a marathon, not a 100-meter dash, so the elevation level of your thighs shouldn't be exaggerated.
Runner's discipline - If it's your first run and you notice a lot of people passing you by, then don't feel pressured. Don't attempt to catch up with them, or you will easily run out steam. Reserve the fuel in your tank as you head towards the last stretch. Focus on yourself, enjoy the run, and finish the race.
Keep on challenging yourself - I have had five 10 kilometer runs, and I have constantly improved my finish time record by 5 minutes after every race. From a finish time of 1 hour and 20 minutes for my first 10K, I trimmed it down to an even 60 minutes for my last. Always challenge yourself to do better, until you have reached your threshold. Set a higher target which will direct your efforts.
Look for running buddies - It would be a great help if you could find someone who share the same passion for fitness. Encourage your friends to join you in this routine. After all, running is the cheapest form of exercise. All the sweat poured from running regularly will pay off.
Run for the right reasons - Run because you love to run. Enough said.