The key to managing my son's behaviour has really been setting expectations and following through on them consistently. He's almost three and very vocal about his wants and needs, so we've had many conversations about how some behaviors are acceptable and will be rewarded, and others won't be tolerated and have consequences.
We use a simple star chart system which has worked wonders for us. We sat him down and explained that if he wanted to earn stars and eventually trade them in for rewards, he had to follow the rules we would set together - things like sharing toys, speaking politely, no hitting or biting etc. We also incorporated natural consequences into his everyday - so if he refused to share his toys, we took the toy away temporarily because obviously, you can't play with it if you won't share!
We made the chart together, with him choosing the rewards and helping stick on the stars, which was fun for him and also helped him understand the process. He's really responded well to it - of course, there are still daily challenges, but it's given us a great framework to refer back to and has taught him about consistency and following through too!
It might seem simple, but it's worked really well for us so far and helped keep tantrums at bay! Would love to hear your strategies too!