Start early with age-appropriate books like Little Owl's Egg, The New Baby by Mercer Mayer, or I'm a Big Brother/Sister by Joanna Cole. Involve your toddler in preparations — let them pretend to care for the baby through play. Avoid saying things that create pressure like you need to be a big boy now. Resources like Siblings Without Rivalry by Adele Faber and the Good Inside workshop on new sibling transition are highly recommended by parents who have been through it.