I have a dog and he's never met chickens before. In the near future I plan on getting chickens so I'm wondering how you would introduce a dog to chickens?
(Personal opinions here. Other methods could also work fine.)
I would start with some dog training, before the chickens are ever present.
A very useful command is "off" or "leave it," with the meaning "do not put your mouth on that." After you first teach the command, you can practice with things like a bit of food dropped on the floor. The idea is for the dog to not touch or grab the food (or later, the chicken.)
I would also try for a good down-stay.
To first introduce the chickens, I would have one person hold the dog, and another person hold a chicken. Let the dog sniff the chicken gently, but not grab/bite the chicken ("off" or "leave it.")
Also practice any commands you like in the same room where the chickens are, or in the yard near the chicken pen. This helps the dog realize that he must obey, even when those exciting fluffy things are present.
Later when the chickens are not quite as new and exciting (maybe in a few days), you can have the dog practice a down-stay somewhere near the chickens (near the brooder, or near the chicken pen, or on the lawn while the chickens are loose on the same lawn.) Of course you should have a leash on the dog at first, and either have a person hold the leash or tie the leash to something, so if the dog breaks the stay he cannot go happily chasing chickens. You can work toward him being reliable enough to do it off-leash.
Later yet, you can take the dog with you while tending the chickens, maybe on a leash attached to your belt so you have your hands free. Reprimand him (gruff or scolding tone of voice) if he tries to grab or chase them.
Some dogs will never get past that point, while some other dogs will go on to be completely trustworthy when loose with chickens. Also, different dogs learn this kind of stuff at very different rates. I cannot predict how it will work with your dog. It's mostly a matter of controlling the dog, letting him know what you expect, and then adapting your own plans based on how the dog is doing.