When you are presenting your dog at a Dog show, the judge does not care to watch your dog snarfing down and chewing his bait. The Judge wants to see good expression and attentive manner, not the goober and slobber associated with a dog who is eating. Bait is exactly what it means: bait ( a lure). If you teach your dog as a puppy to bait correctly, then he will stand in the ring and stare at your hand, offering a look of intense concentration, quizzical interest and anticipation...a look that is expressive and will capture the judge's eye. You can train this easily. Get the puppy's attention first by giving him a treat or two just so he knows you have it in your hand. Do this on a grooming table. The dog will not try to jump off if he is getting treats and it will teach him to stack at the same time. After he has had a couple of treats, close the bait into your closed hand. If he tries to nuzzle and/or lunge at your hand, tap him gently on the nose with your closed hand and tell him "wait"! Then quickly, after he has looked at your hand for even one or two seconds, give him the treat. Keep this up and he will hold it for longer periods of time and he will begin to watch your closed hand. Lengthen the time to five seconds, ten seconds, one whole minute and always give him the treat.
In just a few days, your puppy will look fixedly at your hand. You can get him to look wherever you want just by moving your hand. Eventually you won't need a treat in your hand and you won't need to have a closed fist either. Combine the training with the word you want to use in the ring for getting his attention; that word might be "wait" or "watch".
Many handlers will carry a toy, especially if they are showing a cute little toy dog and they will bait the dog with the toy. This is fine; the toy can be used in exactly the same way that the bait is used. Often a toy can be thrown out ahead of the dog or bounced up and down in the hand, to lend even more expression and anticipation to the dog's expression. Some judges really like it if the dog even barks or leaps into the air for a toy, however, it is usually best to scout out this sort of thing ahead of time and know what it is the particular judge might be looking for.
In any event, the use of bait or a toy is specifically for the purpose of showing off the expression of the dog. If your dog can give you the perfect "look" at just the right time, it can be the exact thing that finishes the dog to a win. However, if this "look" is not there when the judge is looking, you might as well not have bothered. So one of the other important things to remember is that it does no good at all to train the dog to be expressive for the bait if you do not pay attention to the judge and make sure that both you and your dog are performing perfectly just at the exact time the judge is looking at you!
