Running form questions

Hi all, I have never been much of a runner, but lately I have been running on the treadmill at the gym for some cardio exercise. The past couple days my knees have been hurting, and I suspect poor running form as the culprit, so I had a few questions that I hope some of you with more experience could answer. First of all, I think I overextend my stride, so that is something I will try to work on. Also, I am going to start running on the street to see if the treadmill is contributing to my poor form. I was running on a treadmill near a mirror the other day, and I couldn't believe how ridiculous I looked! I seem to swing my lower legs out in a semi-circle before planting them, and I think I land too much on my heel. I also noticed that I put my feet down one almost directly in front of the other, and I was wondering if this is normal/acceptable, or should I try to keep them more in alignment with my hips? I am not pigeon-toed normally, but I tend to point my toes in a bit when I run, should I straighten them out? I usually wear shoes without any arch support for daily use, but I have some running type shoes with moderate arch support for when I go to the gym, and have been wearing them when I run. Is this helpful, or is it a hinderance, do you think? Any tips you might have on what to correct, and how to do so are greatly appreciated. Thanks in advance. : )