In addition to doing 2D animation I also work with the open source, free, 3D animation software - Blender.
There is an excellent tutorial they have in conjunction with the program that delves into walk cycles and it presents it more as 2D to explain contact poses and several other key factors.
I immediately saw it's usefulness for users of AS. I know the topic has been discussed on this forum and I wanted to share this additional resource:
http://www.idleworm.com/how/anm/02w/walk1.shtml
Tutorial on walk cycles
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