Boards
Wash by hand, dry standing up, and oil the board when it looks thirsty.
A solid-wood board will outlast the knives you use on it if you keep water off it and oil in it.
Every day
Wash it by hand with warm water and a little dish soap, then wipe it dry and stand it on edge to finish drying. Never soak a board, never leave it in the sink, and never put it in the dishwasher. Heat and standing water are what crack and warp wood.
Every month or so
When the board looks pale or dry, it is thirsty. Rub in a food-safe mineral oil or The South Farm Board Butter with a cloth, let it sit an hour or overnight, then wipe off what did not soak in. A new board wants oil more often; after a few months it settles down.
Knife marks and smells
Knife marks are the board doing its job. A light sanding with fine paper and a fresh coat of oil takes them back. For onion or garlic, rub the surface with coarse salt and half a lemon, rinse, and dry.
Cheese and charcuterie boards
The same rules apply. Wipe them down after a gathering, do not let cheese sit on them overnight, and oil them when they look dry.