Make it like pudding
That is, sweetly wholesome, rich in consistency, a little wobbly. The components of your nightly routine should be calming (think reading, not pre-bed gymnastics). They should make your child feel good (think a warm bath, a back scratch, a glass of milk). The particulars, however, matter less than that they follow a predictable order. When kids know what's coming next, it helps them feel more secure -- and therefore act more agreeable. There's less protesting about getting into their pj's before they can have a bedtime snack if that's how they do it every night.
This makes life easier for you, too, obviously. But leave a little wiggle room by cutting some parts short (the bath) while making others longer (an extra book or song) -- the wobbly part of the pudding. Just too pooped? Let it go. Skip the bath if nobody's dirty and read six books if you're having an especially pleasant snuggle. Keep your eye on the prize: sleep!
Be the leader, not the follower
Let bedtime flow willy-nilly, and that cup of water you kindly fetch one time becomes a standing order. One evening you help your baby say night-night to her teddy bears. The next, it's good night to all the rest of her stuffed animals. A week later, you're bidding more bye-byes than the matriarch of a seven-generation clan at a reunion.
Sanity check: If your nightly routine is so long and exacting that you'd have to write it down for a babysitter, it's time to pare back. Choose the parts your child likes best, and every night or two cut out another bit. It helps to casually announce the evening's "menu" at the start: "Okay! Time for bath, then pj's, then Mommy will tuck you in and read you a story." If your child wants something added back, stand firm. A complicated bedtime is like any bad habit: Just as it was started, so with perseverance can it be stopped.
Choose lullabies with care
I'm no Alicia Keys, but each of my kids wound up with a signature "song" sung only for them at tuck-in. It's just a little mommy-time ditty -- short, sweet, calming, and pleasant to sing. With Henry, it was "Home on the Range." Eleanor favored "Twinkle, Twinkle Little Star." How I went awry with my youngest, though, I'm not sure.
One night when Page was sick, I sang a medley of every Christmas carol and Barney tune I could think of, including a long, slow folk song called "The Water Is Wide." That was three years ago. "The Water Is Wide" has been requested almost every night since. I could almost ignore the fact that it's a rather cheerless song about love that "grows old and waxes cold" if it weren't also so slow and long that my patience waxes cold, too. And, yes, she protests if I skip any of the verses or try to speed up the dirgelike tempo.