we got a couple of books for DS1 ("my new baby", "spot's little sister" etc) and would read them all together ...

lots of kisses and cuddles for "baby" while in mummy's tummy ...

lots of age appropriate explanations ...

DS1 and DS2 "exchanged" gifts at the hospital. If DS1 was older, we would have got him to pick out a prezzie for his new brother

lots of books to read to DS1 while I feed DS1, so we can all sit together on the couch, so he doesn't feel excluded ... I actually have a little kiddie's Ikea table set up next to me with stuff on it, so I sit longways on the couch, DS2 is propped up with pillows, and DS1 sits between my legs and the back of the couch, so he can "help" and cuddle DS2 during feeds, etc.

we also got a special box with new things (playdoh, a car, a little soft toy, etc) which is *only* for feeding times, so if he doesn't want to sit with us, he has his own very special things to do at that time ...

keeping some things the same - 1-on-1 baths, etc, lots of cuddles and skin to skin time, etc.

and lots of time making sure that he gets 1-on-1 time with each of me and DH, so he doesn't feel like he's been ousted at all.

HTH