i branch mine, 3 blocks between tunnels, and i take the tunnels onwards as far as they will go. you get more ressources per area if you keep the tunnels closer together, but more ressources per block mined if you spread them out. depending on mood i'll explore caves, lava i might bridge over, but i don't do mineshafts, i get lost and/or killed in those.
torches always on the right, that way i can't get lost, just keep the torches on my left and i'll get back to the stairs.
but i haven't actually gone mining in ages, and the only ressource one gets from mining which i'm running low on is lapis lazuli. i do spend time regularly clearing deserts of sand, or walking the abyssal plains collecting gravel, but that's different