My son and I have established a really good routine for homework and study, plus we do plenty of extra work for fun. Early on, I established the idea of learning being fun, and it stuck. He does all the typical kid stuff, too, so it's not as though he spends all of his time with his nose in a book, but he does like learning new things, which keeps him ahead o the curve in school.
My wife and I keep in touch with his teacher, as well. We're on a first name basis, and we volunteer when we can. Being involved like that is the most important thing of all.