NO MEANS NO

Sammy had her first temper tantrum a few weeks ago.
She  was rolling around the kitchen in her little red corvette and kept trying to touch the garbage can. I kept telling her no. Pull her hand back. Push the car back. But she kept at it. So I finally took her hand and popped it. You'd have think I'd given her a round of vaccines. 
Joey is almost four now. And we have a variety of discipline tactics available. Look at the wall, taking away a toy or TV time, simply sitting her down and explaining that we are disappointed with her behavior. And, occasionally, a quick pop on the hand or a bend over the knee spanking. But that is because she is old enough to understand and communicate with. 
I firmly believe that babies need to listen. Not just for your sanity, but for their safety. Today, it might be the garbage can (which is also very much about their safety) tomorrow it might be running into the street. NO needs to mean NO. And since their don't yet understand what you're saying, a pop on the hand is very effective. They simply HAVE to obey. It's not a word I like, but it is simply true with little ones. 
Sam is beginning to understand it now. When she reaches for the garbage can. (It is her snake in the garden of Eden, I tell you!) When she flails around on the changing table, when she grabs a handful of mama's hair... She is getting a stern no and you can see the cogs in her head working behind the light in her eyes, she is starting to understand one of the most important lessons of babyhood... NO means NO.