1. Stand your dog in front of you -- you don't have to formally stack him -- and lift up each of his legs. Note if one leg is harder to pick up than the other. Go to the other side of the dog and repeat because many dogs lean away from you as you enter their space. (Just realized this today, actually.) This is the step that led me to discovering Wall-e's lameness.
If one leg is harder to pick up than the adjoining leg (in Wall-e's example, the right rear leg felt heavier than the left rear leg), then pay close attention to the leg that feels lighter for the rest of the test.
2. Look at how your dog is placing his weight; look at his front feet and his rear feet and notice if he's shifting his weight to any of them. Also notice if he's placing one feet behind or ahead of the other one (for example, if he's putting one rear foot ahead of the other rear foot). If he is, remember it for Step 4.
If your dog is putting more of his weight on one leg than the adjoining leg (Wall-e was shifting his weight to his right rear leg and putting less weight on his left rear leg), pay special attention to the adjoining leg.
3. Gently flex each leg through its natural range of motion. Make sure not to stretch past what the dog could do himself.
If your dog is showing any signs of resistance or pain in a leg, pay attention to that one.
4. Release your dog and then reset him after a few moments. If he was placing a foot behind or ahead of the other one in Step 2, notice if he is doing it again.
If your dog is always putting one leg ahead of its opposite/adjoining leg, that could be a sign of lameness in that leg. You can't really use this step without using the other steps, but it can help clarify lameness if you weren't quite sure before.
5. Walk and trot your dog down a hallway. (Don't formally heel the dog.)
I find that taking a video of this really helps (well, video helps with everything!). Note if there's any abnormality in your dog's gait; limping, carrying the head too high or too low.
Wall-e is still lame, unfortunately.