1. Hitting. If she's not happy with someone/something she hits it/them. It started with her just swinging at it/them, but has now turned into full on slapping or today - close-fisted hitting. Not cool, dude.
I try to catch her hand/arm before she makes contact, bring it down to her side and tell her either in her ear or in her face while looking directly into her eyes, "No ma'am. We don't hit when we're mad."
2. Head butting. This usually happens if she's sitting on my lap and reaches (repeatedly) for something I won't let her have. IE: A knife at the dinner table. If I have already told her not to touch something a million times and then restrain her hands - usually by holding her hands in mine - she gets frustrated and will throw her head back into my throat/chin.
Again, all I know to do is to tell her "No ma'am. We don't do that. That hurts." If she continues to do it I set her down on the floor (if we're at home) and tell her that if she's going to act that way she can't sit on my lap.
3. Yelling/screaming. Usually if I'm not letting her do what she wants - playing in/eating the dog food for example - and I keep removing her from where she wants to be she'll walk around yelling, "NO!!" or other baby-words that I can't understand, but her sentiment is quite clear. She's pissed and letting me know about it.
I normally don't do anything in this situation because yelling at her isn't going to get her to stop yelling and I don't feel like I need to do the whole "inside voices" schpeal yet since she doesn't really do this out in public.
I want her to be able to express herself is she's upset, and I want her to feel comfortable doing so, but I don't know how to get her to do that without being hurtful.
I'm sure some of your kids have/do act this way when they're upset. What do you do in similar situations? What words of wisdom can you give me?