It's mostly about staying positive and using encouragement... the reward is just sort of an accessory.
They are older so you can get away with something that has specific tasks that they get to acheive. Right now we have two columns "to do" and "done" with a line of "stars" at the bottom. Each day our son has to do certain tasks and each one he completes he moves the magnet to the "done" column. At the end of each day he puts a "star" (magnet) in a square at the bottom if he's done all his tasks IN AN AGREEABLE FASHION (without a giant fight). When he gets five "stars" he gets a "surprise".
Below is my reply to another question (about tantrums) and our general approach to rewarding good behavior and how we started using the system, which you'll see has changed a bit. Good luck!
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We have been having some new discipline issues with our three year old and have created a rewards chart that actually has been really great.
Great for him because it keeps him motivated and proud and reminded etc.
It kind of takes care of the discipline issue on its own because A) NOT getting to put a sticker on the chart BECOMES the punishment, and B) you don't have to punish as often because they're motivated to use the chart.
Great for us because it reminds us to keep up on the POSITIVE side of discipline vs. negative. To punish after something has already happened is SO MUCH harder. If you CONSTANTLY keep cheering their good behavior on, you will see a difference. Sometimes it feels excessive to give a kiss or a high five for every little cooperative/good thing they do or bad thing they choose not to do, but it really keeps them on the good behavior end of the spectrum.
With tantrums, it may be a little trickier since they are so impulsive, but I think if she's motivated and if you have the "stop to think before acting" talk, it could work. Be very specific about what the chart is about before you start using it so it's clear to her how she will earn stickers. You probably will have to be a little more conciencious about rewarding for missed tantrums... like maybe if you see a situation where she had the potential to be upset or even whine about something and wasn't/didn't, give a sticker. May have to be more often/overly generous in the beginning so she gets the picture.
Also, we very liberally us the chart as reminders - i.e. "do you think you will get a sticker on your chart if to throw that toy at my face?" It works! You could use the same reminders at the beginning of tantrums or things you might know are triggers.
You can research an age/personality appropriate system for your child and maybe even tantrum specific tips. I found lots of stuff online, including Dr Sears' site. We use a simple but cute chart I found online and just printed it for free. (You can make them too!) It has the numbers 1 - 10 and he gets to put a sticker on a number when he has been a good boy. When he gets to 10 he gets a special surprise. (In the beginning you can introduce a smaller reward halfway through if you think she needs it.) It can be a toy, outing/activity, favorite food.... doesn't have to be object based. You can even give them a choice of things if you want to empower them even more. He usually gets 1-2 stickers on his chart per day. Rewards charts need to be age appropriate and the younger they are the more often they need a star so they can see they are moving up the chart - esp. in the beginning. That said, he often get as much pride by our constant high-fives and kisses for his good behavior. With time I think they become a little less reliant on the chart and the good behavior just comes more naturally. Then you can change the "goal" of the chart to be specific to something else she may need to work on.
You might try to really 'set the stage' for her. Talk about it beforehand, let her help design it, pick the stickers etc... get her really excited so she'll take a lot of pride in it. You can even save the completed charts for her to look at and show friends and family and/or take photos of her enjoying her "surprise" and put it next to the next chart for extra motivation. Right now we have two different designs. I may add more designs since he gets such a big kick out of that alone, it seems like a great way to keep him motivated.
Also, at this age most people say to never take away stickers that they've earned because it sends the wrong message and gets back to the negative end of the spectrum. We have done it only one time when he was being absolutely nuts, but in hindsight I feel like it was an impulse move on my part and not appropriate/helpful.
Sorry so long-winded! ;) We just started and are seeing good results so it's pretty exciting. Mainly for me, it's a great way to keep us parents in the habit of using positive reinforcement to avoid the bad behavior all together.