TERRIBLE TWO'S!!! when do they end??

Man oh man! Do I love my daughter - she is about to be three in may and she in the light of my life... that being said, when do the terrible two's end? Im at my witts end. She throws tantrums almost daily now, over the simpliest thing, literally and if I say NO..... forget about it, she screams like she is being murdered. I mean embarassing is not the word! Taking her out anywhere is almost as painful as delivering her. I feel bad also because i just gave birth to her younger sister, and I dont want to come down to hard on her for just craving attention, but boy she is pushing limits like i have never seen before -- i am open to any suggestion, PLEASE!