I don't know about older children, but toddlers often get more agitated as they get more tired and by the time they are in bed it can take a while before they actually sleep.
I often read that taking a bath before bedtime helps toddlers to calm down, but this doesn't work with our child (actually it's counterproductive). Another standard technique is reading a book, but he likes it so much that once we finish one he just want another one and another, ...
So what other ways do you suggest for calming down a toddler before bedtime?