Verbal commands ("voice aids") are common in bio-equine training and are easily adaptable to ponyplay. A verbal command consists of both the word(s) spoken as well as the manner in which they are spoken. Moreover, verbal commands are not limited to English words and can include "clucking" and other sounds. Voice aids augment rein aids and leg or crop aids.
In addition to the actual spoken word, the tone of voice is critical. Saying "bad boy" playfully (or conversely screaming "GOOD BOY" in an angry voice) can give a mixed signal. More often than not, your pony will react more to the tone of your voice than the actual words said - believe it or not, this does in fact apply to humans nearly as much as it applies to bio-horses. Thus, be consistent in your use of verbal cues to prevent your pony from becoming confused.
Some of the most common verbal commands your ponyboy or ponygirl should know:
While your human pony will probably understand more words than just those listed above and could respond to more complicated commands, it is still useful to know the common voice aids used in bio-horse training. This serves to keep the scene realisitic (if that's what you like), but it is also useful if you encounter a new pony at a kinky event - most of these commands are understood by human ponies even when they enter pony headspace.