Hello S.,
I have a 21 month old, she has been where your child is. She would say no-no and go to hit at us if we told her she couldn't have something, or took something away, lay herself on the floor and scream, like I had just did the worse thing you could imagine. I finally started with asking her when she had something I didn't want her to have, like my cup of sprite, or my phone, etc.... I would say "May mommy have that please" and tell her as she was standing there, "That is such a sweet girl" in a soft spoken voice, and she would bring it to me, and hand it over, then I would say "Thank You" and ask her, you want to play with baby, (which is her baby doll) to get her mind off of what she just handed over, so she wouldn't try to take it again. Believe it or not, this started working. When she would hit, I would give her a very sad look and tell her, that hurt, and say to her, "tell such and such your sorry and give them a kiss" or "tell mommy your sorry and give me a kiss" when she did this, I would change my sad face to a smileing face and let her know she did well, and she started catching on, that hitting was not nice and you have to appologize for doing that. It worked also. Oh, and when she threw a tantrum, laying on the floor and would cry and kick her feet, I tried to pick her up and she would be angry and get louder, I finally would sit by, and tell her when she is done, I would hold her, then I would give it a few minutes, let her scream it out and then ask, are you done, if she continued, I would slowly get up, go fix her bottle, and then come back and tell her, okay that is enough, it is nap time, and I would lay her down in her crib and make sure she had her passy, and tell her I love you, and then I would walk out, close the door and stand by to see if she stopped, Not letting her know I was just outside the door, eventually after 3 minutes, it always did stop. She had soon stopped, knowing what I would do if she threw a tantrum. It is hard, but you have to let her know, that you are not going to let her behave in that manner. Good Luck, I hope this helped.