Advice for new baby?

Hi! I’ll keep it short. I have a son who will be 6 in a few months. My husband (no kids of his own) & I decided to start trying at the end of the year. He has been in my son’s life since he was 3! I told him everyone prepares you for the baby, the smallest duration of age, but not the kid & he’s been an amazing stepdad!

I wanted to ask this sub specifically for any advice or things they wish they knew? I am the primary parent on a typical split with my son’s dad if that helps.