When do we start disciplining our kids? And what method is good? My baby is going to be 9 months. Is it too early?

You can discipline by being firm with them first.It's best to start from young. Secondly, whenever they do something wrong, be firm in your tone. You can consider using a certain facial expression when you are angry so they would know that mummy is angry without you having to raise the voice. After disciplining, it's best to explain and talk to your child to let her know why you are disciplining her for certain actions and all.