D..
Give her ONE warning, and then go put her in her room. Don't let her come out until the tantrum is over, no matter how much yelling she is doing. Even if you have to put a lock on the outside of the door (very high up). Don't let her know you are outside the door. If she thinks you are not there, then she doesn't have a captive audience.
NEVER give in to what she is having the tantrum over. Ever. You have to teach her that she LOSES by having a tantrum.
If you are out and about, pick her up and take her to the car and strap her into her seat, and stand outside the car. Don't sit in the car and listen to her crying. When she gets home, put her in her room for a half hour and tell her that she has lost dear privileges because of her bad behavior.
If she is screaming for something in the store, buy the book "The Berenstain Bears Get the Gimmees" (you can find it at Amazon). It is a terrific book you can read together for years and she will GET that having a tantrum in the middle of the store is ridiculous. AND that she won't get what she wants anyway.
To help you both, make sure that she eats breakfast, mid-morning snack, lunch, afternoon snack and dinner, at the same time every day. Nap should be at the same time, and bedtime too. She needs transition notice when you change activities. And don't take her out if she hasn't had a snack or when she is tired.
Be 100% consistent and don't give in to her when she has tantrums, ever. She will stop if you don't put up with it.
Good luck,
Dawn