This is for people who are not expert trainers.
An important training target is food-proofing your dog. The target is to have your dog take food ONLY from you or from one of your family members.
The implications for NOT doing this are obvious, including the object lesson of a dog that was taken recently by being offered a hot dog by strangers. Depending where you live, I am sure there will be also situations when poisoned food will be offered for a variety of malicious reasons. I will leave it up to you to conjure up images of such potential situations, including a neighbor who happens to hate your dog or brats who do it out of spite or entertainment.
The premise is that if you teach your dog not to take a variety of foods from anybody but you, the dog will be able to generalize to all foods and to all people. This can become an issue if you leave town and have to leave the dog behind with a friend or in a kennel. But, that is relatively minor issue and can also be trained. My dog is either with one of us or a friend veterinarian who attends to him anyway. Nobody else.
Start by squatting or sitting with your dog, holding his/her leash with your dominant hand (with your thumb through the loop), the other hand grabbing the leash about a foot or a foot and a half away from your dominant hand. The non-dominant hand thus becomes the “leash snapper.” For training I use either a six or five-foot leather leash. Regular collar.
Have a friend or somebody who visits your house frequently throw some desirable food in front of your dog (hot dogs, treats, raw meat, cheese, etc.). The dog natural tendency will be to sniff the food and want to eat it.
As soon as the dog orients toward or sniffs at the food you snap the leash with your non-dominant hand (doesn’t have to be a hard snap, more like setting the hook in a fish’s mouth when fishing with a flexible rod) while saying “NO!” in a low and commanding voice. The snap and the “NO” occur simultaneously. As soon as the dog looks at you, you say “Good dog” or whatever you say in praise to your dog, this time with a higher and kinder voice. You can also frown with the “No” and smile with the “Good dog.” I do.
You will have to do this exercise with a variety of foods over several days. Use different people and also have them throw food over your dog yard’s fence with or without you in the yard. My dog is never alone, but I did the exercise by standing on the deck that is over the dog run. Use food that is normally attractive to your dog.
As usually, what’s critical is consistency and repetition.
I also used method to break fixation on dogs, cats, or anything that grabs Sándor’s attention away from me.
Remember: your dog needs to be trained not to do anything for which: 1) you did not train him; 2) you do not allow; 3) has not earned the privilege. For instance Sándor has to sit in the dining room and wait for me to serve his yogurt in the kitchen. Since cutting up carrots and apples and mixing up several types of kibble takes time, he has to lie down. He can start eating only when I say “OK, you can eat now.” Thus, he earns the right to eat by being patient and by lying down.