1. Move the centre of gravity forward until it lies just outside the area of contact with the ground. (lean forward).
2. Move a prop (leg) under the new centre of gravity to bear the weight.
3. Bring the rear prop (leg) forward since it is no longer load-bearing.
Repeat from step 1
NB
Swinging the rear prop/leg forwards (like a pendulum) has a problem since it would need to pass lower than the ground surface. There are three ways to overcome this:-
a) Introduce a joint so that the prop/leg can be raised as in animals ansd robots.
b) Raise the prop/leg by means of cams. (toys)
c) Tilt the body to one side to let the prop/leg swing round. This introduces a waddling motion to the toy.
Thanks gen2, I am trying to figure out your answer,I dont think its simple, but let me think about it some more and I will let you know if I get stuck.
Thanks