For those who have second kids, how and when did you start preparing your elder kid for the new baby's arrival?

I started to prepare my elder kids once I found out I am pregnant by bringing him/her to go for gynae check-ups and tell him/her about the ultrasound pictures. Also, I bring my kids to buy clothes, toys and other baby necessities together and let them choose the designs. During the normal days, I will ask my kids to help me to apply stretchmark lotion on my tummy, also singing to the baby in the belly. Once I feel the baby's movement, I will quickly ask them to come and feel it too. My baby no.2 likes to sleep on my tummy at night to feel the baby. Also, I borrowed books from library for them to understand what to expect. It is more for my 2nd child as he never experience to have a younger sibling before. For my eldest daugther she is more understand of what is really going on and thus normally she will request me to show videos of childbirth (animated one and not scary one) to her.