My daughter the SCREAMER!!!

For those of you that don't know...my daughter is a screamer. AAGGHHHH!!! Some days are good days & some days I feel like the lady in those old Calgon commercials... the one where you see the lady & swirling all around her head are the crazy things in her life like the dog, kids, dishes, etc. And she yells "Calgon take me away". Gee, if only it was that simple.
So, back to my daughter - she really is a sweet child when she wants to be - but man oh man can she turn on you & it's like looking at the Exorcist - I am just waiting for the day when her head spins around & green puke comes flying out of her mouth. I have been reading the book Baby 411 and it has a lot of really good tips. Some say to ignore it, some say it's just her temperament, & some say she will out grow it. HELP HELP HELP please - any tips or suggestions???
Is this just the "terrible twos"? I have had people tell the the "terrible twos" last until about the age of 4. Lordy, lordy, lordy - I don't think I will make it. Should I call the psych ward & tell them to reserve a room for me? Thank goodness all the kids I watch aren't screamers. Any my dear hubby wonders why it takes me 2 hours or more at the grocery store. I guess that's my "calgon take me away" moment.