How should I angle my foot throughout a pedal stroke?
For most people the advice goes that you keep your foot as flat as possible. There are some riders that ride toes down (even some famous ones in the Tour) but they've had a coach determine that in their specific case there is benefit to riding toes down.

It's unlikely that you can keep your foot entirely level as it comes over the top of your pedal stroke but it should be level through the power stroke and around the bottom as you pull back on the pedal to spin.

As a response to one of the other posters, be very careful about ankling. While it is touted as a great thing many coaches feel that it does nothing and is an old wives tale. Some even feel it's harmful to you. I've attached some links for futher reading on the subject.


http://www.sheldonbrown.com/gloss_an-z.html#ankling
http://www.sheldonbrown.com/brandt/ankling.html
http://www.pezcyclingnews.com/?pg=fullstory&amp;id=4812
http://www.roberts-1.com/b/pt/ankling/discuss/index.htm (good links in post)
http://triandrunsports.com/triforum/index.php?topic=2362.0
http://www.bicycling.com/training-nutrition/training-fitness/perfect-pedal-stroke


From the reading above, and other articles on the subject, I'm inclined to recommend against it. At the very least talk to a medical professional who can look at your pedaling technique and biomechanics and advise properly.