The following website has the article - Approaches to Animating Quadrupeds: The Walk Cycles, which bacially gives a guide to how to animate a quadruped walk cycle.
http://www.rocket5studios.com/tutorials/approaches-to-animating-quadrupeds-the-walk-cycles/
http://www.rocket5studios.com/tutorials/approaches-to-animating-quadrupeds-the-walk-cycles/
This is an image from the website above which helps to understand what order the feet touch the ground in different movement cycles. This will help a lot when thinking about creating my own quadruped walk cycle.
Here is a similar diagram that shows when each foot is off of the ground. By looking at the diagram, you can see that when a foot lifts, the one that lifted before hasn't get gone back on the ground. This means at times, there are only two legs on the ground.
