Let the older sibling buy a new outfit for the baby girl with a matching gift for the older sibling. If the older sibling is a girl, the dresses or shirts can match. If the older sibling is a boy, he can give his new sister an outfit that has matching socks or a hat for him. A number of children's fabrics come in unisex patterns and colors, so if the parents want their children to dress in gender-specific clothing, the unisex fabrics allow the older child to enjoy giving his new sister a gift that he feels connected to as well.
Shop for a stuffed animal for the new sister that she can "take care of" together with the older child. The older child can "show her" how to bathe, feed and clothe the stuffed animal. The older sibling will enjoy playing the role of the surrogate parent, guiding and teaching her new little sister as she shows the baby the intricacies of caring for the new creature.
Purchase a book that the older sibling can give to the new sister. The sibling relationship can get off to a good start if the parent cuddles both children while they "read" to the new baby. Depending on the older child's age, some good children's books that a toddler or pre-schooler can also enjoy include "The Snowy Day" by Ezra Jack Keats, "The Very Hungry Caterpillar" by Eric Carle, various editions of Mother Goose Nursery Rhymes and the ever-popular Dr. Seuss books.
Encourage the older sibling to "present" the new sister with the crib as the older sibling graduates into his new bed. The process of moving into a big-boy or big-girl bed can turn into a ceremony, allowing the older brother or sister to help "put" the new baby sister into the crib where the older child used to sleep as he receives a new bed.