Running form

I've never been able to tell if I'm a heel striker or a mid-foot striker or otherwise when I run.  I probably wouldn't care in the grand scheme of things except that (a) I am a slow runner and I wonder if my form has something to do with that and (b) I tend to look down at my feet when I run and I am a slow runner and I wonder if my form has something to do with that.

After way too many race pictures that looked like this --

-- where I'm kind of hunched over and leaning forward and looking down at the ground with a very short stride, I decided for my last race that I would make a conscious effort to improve my stride.  Shoulders back, head up, slightly longer stride.  In particular, not to look down at the ground, which I tend to do when I get tired.

I did pretty good overall --

-- although I did have to look down at the ground during the part where I got really dizzy, lest I trip over a tree root and/or a buckle in the paved trail.  Or pass out, throw up, fall off the trail.  (It was really damn hot.)  I felt a lot more like a runner, rather than a plodder, by keeping a more upright stance.

I still look like I'm a mid-foot striker, though.  I've read that that is easier on the lower legs, making you less prone to injury.  I've also read that leaning forward slightly helps you retain your forward momentum; it's one of the things chi running advocates.  Lastly, I've read that a shorter stride also helps with injury prevention.  No matter which is correct or better or whatever, I like the look of the second picture over the first.  Even though I was trying not to fall down, trip, pass out, throw up, or fall off the track.

Anyone have any running form tips?

Cheers,
the CilleyGirl