Both my kids went through tantrum phases early, around 10 months old and at that age it was very easy to deal with. I simply told them they could have their tantrum and that they could come out of whatever room they were in once they calmed down. The phase only lasted a week at most. My daughter is now almost three and my son is 16 months, neither one have thrown tantrums since.But, with older kids it can be trickier. One thing I've always done with my kids that helps avoid tantrums is to let them make decisions whenever it's possible. I let them choose between two shirts/snacks/books/etc. as often as I can. Allowing them to make small decisions helps them feel like they have control over things in their lives. Most tantrums really aren't about kids wanting to get their way at that specific moment, it's about a general lack of control when they're learning to become independent. Letting them choose things for themselves shows them not only that they can make decisions, but also that you trust them to make the decisions. Because of this they are more likely to listen to your rules about behavior, bedtime, etc.Next time you're in a situation where she is misbehaving tell her how you would like her to behave and what will happen if she doesn't listen. Give her the chance to decide for herself what she wants to do. Give her two chances to change her behavior and if she doesn't, follow through with the course of action you described. If you're in public, leave the store. If you're at a playdate, leave. If she's throwing toys, take them away or give her a time out. Make sure whatever you do is appropriate and don't yell or get angry and don't spank.