The best thing to do, I think, would be to go and look at some references of people running. In fact, I've got a real good example for you right here
http://photo.ucr.edu/photographers/muybridge/index66.html (warning:nekkid man ahead) Like every other area of art, animation requires studying from life to improve so take note of how each leg is positioned during each point in a single cycle.
I'm new to animation as well, only been going at it for maybe 1/2 to 3/4 of a year now, so I'm reluctant to really impart any wisdom since I'm pretty much guaranteed to learn in the future that I was either completely wrong or misguided in many areas. However, back before pixelation tooks it's latest nose dive, Sals(Adam Tierney) always posted the same advice to people looking for critique for animations. When I began to take in this advice, I noticed a dramatic increase in the quality of my animations. This increase being that my animations went from crappy-horrible to better. It's his advice that enabled me to make the leap to where I no longer feel completely flustered when starting an animation.
Anyways, Adam's advice basically goes something along the lines of: "keyframes, keyframes, keyframes". If you wanted to, you could animate a 60 or 120 frame running animation just so that you could show the leg in every possible position that it creates while running. There really wouldn't be much point however because it's not like we would notice all those frames. To express movement, you just have to place focus on the key gestures that indicate movement, and these key gestures become your keyframes.
So, try not to create your frames by thinking where the leg will be every .1 seconds.
[. . . . . . . . . . .]
Decide on which frames will indicate the running action better and focus on them
[... ... ...]
Here's an example Adam used once. I recommend saving and taking a look at the individual frames. You'll notice that when the little guy leaps through the air, Adam doesn't place him at the various points he would appear at in the air. Instead, Adam has him pushing off the ground in one frame, at the peak of his jump the next and in the frame following has the guy landing on the wall or floor. That's really all that Adam needs to let us know that the little guy is jumping and landing. If he wanted to Adam could add some more frames to smoothen the jump, but he wanted to show just how valuable keyframes can be when used effectively.
I also made an attempt at an edit for you. Main changes are to his legs which I made to resemble a real person's run more. I kept the hand positions the same to keep with how you imagined them. I did add a little bounce to them, though, as the lack of movement in your version was slightly distracting and a bit odd. If you don't like it go ahead and change it back.
[mine] [yours]
