Great topic!
I think the most important thing a parent can do is to live as an example of a true Christian. It doesn't matter if you bring your child to church if you're not displaying God's love at home.
Have regular devotions with your family so your children know what you believe and not just what they hear in Sunday School and church service.
I know what I listened to and what I read as a child influenced me. Make sure they have Christian music to listen to and Christian books to read (it doesn't have to be to the exclusion of all else, but make sure you know what is going into their minds).
My daughter is 4 1/2 months old so at this point, I sing Christian songs and quote simple verses to her.
Deut 6:4-5,
Psalms 23,
Psalms 100.