Problem: You've got ten seconds to make a move. You're in that precarious pre-tantrum state, either looking at a cross-armed, sighing toddler (since when did they decide they were teenagers?), or you're hearing garbled speak over and over again and you can't make out the meaning no matter how hard you try. Whatever the cause, you know your time is short. The end is near. You've got to act fast.
Solution: Distract them. But not with the old "look at this, isn't it so fun?" Distract them with something they can and want to show you. My husband did this yesterday. It was brilliant. One of our daughters loves to sing, the other loves to dance. The dancing one is always asking us to watch her spin and sashay and it just gives her the greatest pleasure. Of course, I don't connect it with anything. I'm not that quick on my feet. My husband, though, when she started acting out, he immediately said, "Dulce, show me a spin."
End pre-tantrum. She stopped what she was on about, got up, and gave him spins. He kept her doing it for a few minutes until she'd forgotten she was trying to be upset. Then we did the typical redirection they tell you about in the books, that usually won't work for us.
It was amazing.