<p>For recommendations get anyone who can speak to your relevant talents. If you write in your letter about how much you love physics then get your physics teacher. If write about doing poorly in Calc but worked hard, get your calc teacher! I think the purpose of a recommendor is to confirm and elborate on the claims you make in your letter.</p>
<p>As far as length, I did not see any guidelines. One page is a good length.</p>