Are there some quick ways (other that simply running a lot) to learn to spend less energy per minute, given same speed? E.g. trying to hold upper body on same level, or something along these lines?
A running coach can give you specific advice but it won't make a huge difference. Holding your arms high and not swinging them across your body (some would say to throw your arms back), minimizing the twisting motion in your torso, running in a straight line instead of weaving across your centerline, etc.
