Can you give some tips how to run economically?

I think that just comes with time. You'll also notice it helps if you slow down your pace. This weekend I did an easy 12 miler, and I noticed after doing that 22 miler last weekend, the 12 miles just felt effortless. Like when I'm walking, I don't think about that I'm sort of exercising and that I need to keep up a pace or anything. I was just running effortlessly enjoying the scenery. But if I wanted a workout out of one mile I could still get one, if I pick up the pace it is no longer so effortless.

I think in this instance looks are deceiving. I bet a lot of effort is going into their movements even if it looks effortless. Running is hard work! I'll say practice, practice, and more practice. Read some books on different styles of running and experiment with what works for you and you will develop your own style of running that is most economical for your body. Though it will still be work. Maybe join a running group and talk to some of these other runners you admire their stride and style. They will be happy to help you out with what they do.