I’m a big fan of brines and marinades for chicken.
A brine is nothing more than a very salty and sweet solution in which the meat sits for an amount of time. Osmosis draws water out of the chicken because the brine is so much saltier than the chicken. But the chicken eventually reaches equilibrium with the brine, and some of the salt and sugar enters the meat.
This serves two purposes. First, the increased salinity means a faster rate of transfer between the brine and the meat. So any flavorings you add (whole black peppercorns, bay leaves, oregano, thyme, etc.) will have a better chance of getting into the meat than if the salt content were lower.
And second, salt carries water with it. This gives you a little cushion with your cooking because you are less likely to dry out the meat. Overcooking the meat coagulates the proteins and wrings out the water. Salt in the meat helps combat that.
I limit my chicken brines to 3/4 cup of salt for 6-10 lbs of chicken. Any more than that, and the chicken becomes too salty for my taste.
My current favorite is an orange juice brine. I heat one can of OJ concentrate with 1 can of water. Then I add the salt, a couple bay leaves, 1 Tbsp whole black peppercorns, and some sage and rosemary. I let that simmer, then add it to my stock pot with lots of cold water so the chicken doesn’t cook. Then I add the chicken and fill it with just enough water to cover the meat.
After 4-5 hours of sitting on the counter (don’t worry, the high salt content prohibits bacterial growth) I pat the chicken dry, lightly coat it with oil, and grill it.
As for the marinade, I like to make a base of acid and oil. The acid helps break down the tissue and soften it, making it more tender as well as offering more pathways for flavor. The oil adds moisture to the mix.
One of my favorites is a fajita marinade. I zest six limes and squeeze their juice into a bowl. Then I add 1/4c olive oil, some paprika, chili powder, garlic powder, salt, pepper, cumin, and honey.
Whick that together and pour it into a gallon Ziploc bag with the chicken. Let it sit in your fridge for 5 or 6 hours.
In a pinch, store bought oil and vinegar salad dressing or any Italian dressing will make a great marinade.