Oh I had a shocker of a tantrum thrower! She was so bad she basically got no EL! I spent my entire time doing behaviour management with her. She certainly taught me patience!
Anyway the biggest help was banning TV. I used to send her to watch TV when I just couldn't cope with her anymore. It was the WORST idea ever. she couldn't cope with TV and even now years later I have to limit her viewing.
Excersize definelty helps. It is a known mood leveler.
Regular drinks of water helped. As did ensuring level blood sugars through regular small meals.
very important was to set firm boundaries and never ever go back on your word. If you can't follow through with a threat don't say it at all. Consistency is key. If we were heading out I used to talk through the expectations for behaviour before we got out of the car and remind her of them often, remembering to praise any good I saw.
Even after all that we still had regular tantrums and I was often found shopping in Isle 3 while my daughter chucked a tantrum in Isle one alone. I shopped Monday morning and thankfully the staff got to know us and kept an eye on her. One time I even took witches hats and placed them around her while she screamed. She didn't care one bit!
It does get better just be consistent!