Being an ex- cross country dude, I can give you some pointers.
You want to run with an upright body posture. Many times I see people somewhat crunched over a bit. That is no happyiness. It doesn't allow for a full inhale of that wonderful air that keeps you going.
Relaxed arms are key. If you're on flat ground, just run with semi-open fists. Kind of like half-way to a closed fist. If you're climbing a kill, it's best to move your hands open, and "pull back" on the air, kind of like you're swimming. Just something I picked up from the "good" runners.
Stride can also have an effect, but not too much because of the length of your legs. I always found that long smooth strides were the best for long (5+ miles) runs, and more medium were better for shorter runs.
Uhm...don't run on hard surfaces that much. That's one reason why marathoners are normally injured. Long runs on hard surfaces, no matter how good your shoe, will stress the bones in your legs more than you want them to. Find a nice dirt, or gravel path and go at it.
Shoes are important. VERY light shoes. I hope you wear actual running shoes, and not cross trainers like so many people actually do. Running shoes are designed FOR running, so you will be the most comfortable in them. Asics have been my shoe of choice, but of course, it all depends on your preferences. Just don't choose a shoe because of how it looks. PLEASE!!
I believe that should cover it, if you need anything else, just gimme a hollar!
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Sitting in a bridge
Watching the biggest star
Finishing a day.
