What is the best long distance running technique?

Try to think of your lungs as gears. When you go up a hill you will have to breathe more frequently in order to produce enough "rev" when you respire to make it up (also smaller quicker steps).

I find it useful to breathe in time with your steps (i.e one breath in for three steps, one breath out for three steps) or if you are not as fit: quadruple time (one breath in for four steps, one breath out for four steps) - this is useful for going down hills. To accelerate: breathe every two or one steps (same for steep hills).

Using these "gears", you will find it far more easy to fall into that perfect running rhythm. Don't forget good technique: straight line body to head, stride length with legs perpendicular to the ground when they hit, no heel planting - run on the balls of your feet, don't bob up and down, lean forward as if you are falling and extend your legs further out at the back to create more of a "spring".

Hope this helps and happy running!