Mark Twain once said that wrinkles should merely indicate where smiles have been. So instead of seeing a plastic surgeon for a round-number birthday, why not celebrate your smiles? Party planner Colin Cowie likes to mark milestones with rituals. "They focus energy on the person being celebrated," he says. "At a friend's 40th birthday, I asked each guest to write a birthday wish on a piece of silk, then tied the pieces together and draped the knotted garland through the branches of a tree," under which everyone ate dinner. He has also asked guests to write wishes on cards, then placed the cards in a beautiful box for the host. If the above sounds too festive for your mood, Kansas City, Missouri, psychoanalyst Marilyn Metzl says to "go someplace special that you've always wanted to visit." Patty Marx, author of You Know You're 40 When… (Broadway, $9, www.amazon.com), suggests New Zealand, explaining, "With the time difference, you might be able to miss the birthday altogether."