Indoor cats not familiar with the outdoors are likely to get frightened and hide if they wander outside. Others do things they regret, like climb trees then up in the branches become scaredy cats unwilling to climb down. Yet others will find themselves in places like cellars they can’t get out of. It’s much easier to find a lost or hiding cat if it has been trained to meow back when it hears its name called. If your cat is a natural talker, training is quite easy. You’re simply channeling a natural behaviour. Training is much harder if your cat is not naturally verbal.
Have treats handy and when your cat speaks without your asking it to, say “Milly speak”. As it does so give the treat. Evolve this to intermittent rewards and within a few days your cat will ‘speak’ when it hears your command, ‘Milly speak.” Take care if your cat is already loquacious. If it’s a constant talker, a typical Siamese trait, and that gets on your nerves don’t train it to speak or do so because you want to then train it to be quiet. Remember, any behaviour you reward, including meowing will increase if that behaviour is rewarded.
Once you’ve trained your cat to speak on command you may want to train it to be quiet. Do this by requesting ‘Milly speak’ to your already trained talkative cat but don’t give any reward. Instead redirect its attention to something else such as a thrown toy. When your cat interacts with the diversion, give verbal or food treat praise.