I think the marble idea is a great idea. I don't believe in punishing children -the most I've done is take away privileges. When my kids were younger and they were having a tantrum, I would wait for them to calm down and then we would discuss the behavior. Getting angry and negative punishment doesn't teach them how to handle themselves. If it was in a store I would remove them from the store.

Its natural for kids to misbehave and they need to learn how to control their emotions - they're not born knowing how to manage their feelings and its seems like you understand this. You sound like a good parent who's trying hard. Here's a few links:

http://www.amazon.ca/Kazdin-Method-P.../dp/0618773673

http://www.mayoclinic.com/health/opp...sorder/DS00630