I can't seem to shake my former dog-trainer ways. I reserve "no" for both the dogs and the baby for BIG things, things that are immediately dangerous, things that will absolutely hurt them. I've used "no" (really, it's "NO!!!"- it's meant to startle and interrupt, and to let them know that I AM REALLY SERIOUS RIGHT NOW) once with V- she was crawling around and I had thoughtlessly left the cord of the cold, unplugged iron dangling, and she was headed for it. The loud, scary "NO!" is meant to stop her (or the dogs) in her tracks until I can physically redirect. For me, "NO!" is an extension of my hand- when I can't grab them, my voice does.
For minor annoyances, like getting on the couch (dogs) or trying to rip my hair out (baby) I use "eh-eh" or "uh-uh," just a little grunt of gentle reproach, then redirection.
It kills me when people chant "no, no, no, no," to either their dogs OR children without actually *doing* anything to stop the unwanted behavior. IMO, a hey-cut-that-out word or noise should ALWAYS be followed by physical redirection, otherwise it doesn't *mean* anything. Overusing any word dilutes the meaning, so I think it's very valuable to reserve certain words for very important times. (I also only use "Come" with the dogs when I know they'll obey it; otherwise I whistle or use a variation of noises, so if they blow me off, they haven't weakened my one go-to-in-an-emergency recall command.)