We learned pretty early on the farm not to shout "Go!" to get the horse to move. It sounded too close to "Whoe!" which is what you should shout to get them to stop. "Whoe, big fella!" if you're dealing with Silver.

"Giddy-up" followed by clicking your tongue against the roof of your mouth was generally good for initiating lift-up. Digging one's heels into his ribs could also be effective unless the horse was ticklish. Then you might only get the horse-laugh. We never used a whip. Although, sometimes one would slap the horse's rump gently with the end of the reins to get him or her to shift into a faster gear.

Let me end this discourse with the following observations:

She was only a stableman's daughter,
But all the horsemen knew her!

Cheerily,
Charley Noble