It seems like a big mistake to me to get into a contest of wills with a nine-month-old, so whenever he's doing something I'd really rather he not do, my solution is the redirect. "Hey, look at this thing!" is a remarkably effective answer to pulling books off the lower shelves or grabbing the washcloth that baffles the pee fountain during a diaper change or lunging at a sleeping dog who outweighs him by thirty pounds.
But he's started doing something which I feel merits a "No" with some (eventual) expectation of understanding and self-control. Possibly this is wildly unrealistic.
He grabs the glasses off my face, or smacks me in the face, or grabs my lower lip. He's strong now, and I actually fear for the integrity of the glasses, not to mention my features. It's like he's just discovered there's a face there, despite my being in his tiny grill pretty much 24/7, and he's as excited about grabbing for it as he is about grabbing for, well, pretty much every other thing.
So far, my response has been ... Ok, mostly my response has been "Ow! Dammit!" but I recognize this is unlikely to be effective, especially as he finds it highly entertaining. So I've been saying "No glasses," or "No grabbing faces" in a stern voice and holding on to his little hands, which drives him absolutely bonkers. Then I say "Gentle touches," and guide his hand to do just that. So far, no success whatsoever, but I wasn't really expecting any. Sooner or later the light will dawn, I'm sure, but until then I think it's mostly a strategy about venting my irritation in a potentially constructive direction.
Anyway, I'm hoping it's a phase, like the occasional shrieking, that comes and goes rather than continuing until I've won the contest of wills, which: oy vey.