I want to start by saying that in my opinion there is no such thing as an ideal stride that is best for everyone. Individual runners will have to find their own ideal stride. For a good example of this just look at elite runners. Haile Gebereselassie lifts his feet very high off the ground and lands mainly on his toes. While Abdi Abdirahman barely lifts his feet off the ground at all and lands very much on his heals. Yet they both have had a great deal of success with their particular running styles.
Humans are made for running (I mean that literally, check out this article that talks about how running shaped the evolution of humans) and therefore your natural stride will most likely be your most efficient stride, or at least quite close to it. By that I am talking about if you tend to land more on your heals or your toes or anywhere in between when you run. A natural heal striker will most likely always find running at least slightly more on his heals to be more efficient than landing on his toes. That’s not to say that you can’t and shouldn’t work to improve the efficiency of your stride. Running is like most things in life, the more you do it the efficient you will become.
One thing to keep in mind when working on improving your stride is your stride rate. It has been found that the most efficient stride rate is right around 180 steps per minute. Once again, since everyone is different, the ideal number will be slightly different for each person. A good experiment to try is when you are out on a run and in a good rhythm along a flat stretch, count how many times your right foot hits the ground in one minute. Then double that and you have your stride rate. If your stride rate is way below 180 you most likely are over striding and probably landing mostly on your heals. And if you are well over 180 you are probably chopping your stride while running up on your toes. By focusing on either shortening your stride and increasing your turn over or lengthening your stride, which ever way will get you closer to that 180 steps per minute, during your runs you should eventually start to feel like your stride is getting smoother.
If you have any stories of how you have been able to improve your stride to become a better runner I would love to hear them.