I actually wasn't a big fan of getting the older sibling excited about the birth of a new baby. The way I figured it, new babies are pretty darn boring from the perspective of the sibling. They sleep. They poop. They cry. And they take attention away from them. Not a whole lot to get excited about.
My oldest was not-quite-three when our twins were born and I was so worried about him getting neglected and feeling left out and resentful of his brothers. (One baby attracts a lot of attention, but twins are a magnet like you wouldn't believe!) I didn't do anything before the twins were born except to mention it anytime he expressed interest in my stomach or the baby furniture. After the twins were born, I made certain to include him at EVERY opportunity. If a stranger approached to ask a question about the babies, I would introduce them as "these are Alexander's little brothers." This would bring him instant attention and he started introducing them as HIS babies. If I was doing something with my oldest and one of the babies started to cry I would say "I'm sorry baby, I know you are very very hungry but Mama is reading a book to your big brother and I need for you to wait until I'm done." My oldest was mostly potty trained when the twins were born, and every time I would change a diaper I would heave a HUGE sigh and I would say "baby, I really wish you could go pee pee in the potty like your big brother because Mama doesn't like changing diapers!" These small things worked SO well. My oldest felt so special. He'd say things like, "don't worry baby. I teach you go pee pee in potty when you get big like me!" And sometimes he'd give me a disapproving little look and tell me that the babies were hungry right NOW and I could finish reading him a book after a fed the babies. (SO sweet!)