Tips for a new mom

Hi guys, i have two problems here and hope all of you can give some insights.

First of all, what do you guys usually do when your toddler ask for something and when you say no they are throwing tantrum or crying out loud ? How to make sure that your kids can wait patiently?

Second of all, my daughter (16mo) loves to hit her head with her hands to seek of our attention. Sometimes she hits so hard and i'm worried about this. How to stop this? Or do you think this is just a phase?

Thank you