A skill that is often neglected in many personal protection and police dog training programs is the ability to point out or "mark" a specific target. Why is such a skill in a important? Imagine you need to alert your dog on an assailant in public and there happens to be several other innocent people standing around. If you do not have the ability to mark a specific target then the dog has no idea which one of the several people in front of it is actually the "bad guy". In an age of frivolous lawsuits, you can not afford to have your dog make the mistake of choosing the wrong target.
Have your dog sitting in the heel position and with its food bowl (with food in it) a few feet directly in front. Point at the bowl with your entire hand and arm and say, "Mark." Make sure your pointing hand/arm is within the dogs line of sight. If the dog does not look at the food bowl, just calmly repeat the word "mark" as you continue pointing until the dog looks at the bowl. The instant the dog looks at the bowl, give it your command that releases it from the heel position to eat the food. Of your dog was staring at the bowl the entire time, just point, say "mark" and then allow it to go eat.
The next day, place the food bowl in front of your dog, however, slightly to the dog's left and repeat the steps mentioned above. Place the bowl slightly to the right on the following day. Eventually, start placing the bowl farther away and in various spots in front of you and the dog.
Once this has been done for a while, place 2 identical food bowls several feet in front of your dog. One bowl should be to the left of the dog and the other bowl should be to the right. Place a little food in both bowls and see which one the dog stares at. Mark the bowl that the dog is not staring at. If the dog does not follow your hand and look at the other bowl, calmly say, "No" and then give the mark command again as you point at the other bowl. Repeat it until the dog looks at the bowl you are marking and then give it the command that allows it to eat.
Unless you have very good off leash obedience to call it back, I would recommend having a leash on it in order to pull the dog back in case it tries to go for bowl it was originally looking at. Anytime the dog goes for the wrong bowl, get it back to the heel position and start again until the dog goes for the correct one.
During this time, begin to slowly increase the amount of time before releasing the dog to eat after it has marked the correct bowl on your command.
Once dog is proficient at the 2 bowl drill mentioned above, have one of the bowls be much closer to the dog than the other. It will be natural for the dog to want to go for the one that is closer. Mark the bowl that is farther, but when you release the dog to eat, be ready to stop it from going for the closer bowl. The dog will learn that in order to get what it wants it must follow the directions you give.
Now you can take this skill to the training field. Repeat the method used with the bowl except you are now marking people instead a bowls. If you have done your homework, this skill will transfer over to the man very easily. To ensure that the dog truly goes for the man you have marked, find someone that the dog has never worked with. Have your regular trainer stand on one side with the bite sleeve and have the stranger stand on the other side wearing nothing but street clothes. Have the dog on leash, mark the stranger, and give your alert command.