Mine started suffering consequences around two or three. I would give him a little pop/slap on the back of the hand or butt or leg, just enough for a little bit of sting, and say, "Hot, hot!" It didn't take long for him to be able to recognize that when I said, "No-hot!" That meant pain, discomfort, and/or danger. This was handy for steering him away from things like electrical sockets and the like...anything he needed to keep clear of, or any behavior that might merit some correction.
As he got a little older, consequences turned into a 3 way conversation between me, him, and the belt/paddle called a "conference." So I would tell his teachers at school that if he acted up or disobeyed them, to simply tell him that they would call his mother and request a "conference." He would immediately get in line, because he recognized that the consequences of continuing that same behavior, was going to result in pain, discomfort, and/or a sore butt.
I've seen people who's kids were controlling them, screaming and throwing tantrums in public. My son never did that. He tried to emulate that mess 1 time. Just once. He learned very quickly the "consequences" of disobeying me, particularly in public; and any time he forgot, I would tell him-in public, "Do you want to go to the restroom for a conference?" It worked every time. The scriptures are true. Spare the rod, spoil the child. GB