Well, I started serving before I was a Christian. I played in a local church's praise band/orchestra. I was investigating Christianity at the time - didn't really know what to make of it or if it was worth considering. I learned a lot from those people, from meeting with the pastor, and just from observing how they lived their lives. I learned that I was given a gift for music by God and that I needed to use that gift to serve Him at the very least through that gift. Since then, I've continued to develop my musical gift, but also have built on the foundations laid for me earlier. I've taught Sunday School, led music during services @ my local church, led Children's Church, got to spend quality time with our infants and toddlers in the nursery, and have seen people grow in their walk with God.
Of course with all of the above comes the greatest challenge for me - how do I take this great news out to people who've never heard it and are generally apathetic or even hostile to the gospel? God's been laying that on my heart a lot lately. Definitely a whole new meaning to being open/available for service (to me).
BTW, as an aside to the nursery thing - I think the best idea I ever heard was that a silent nursery is the sure sign of a dying church. We had a great thing going where the paid staff would change diapers and attend to the physical needs of the children. As volunteers, our job was mostly to play with the kids, read to them, roll balls, and just love them. It was great to see them smile and laugh and start thinking that this was a place where they could have fun and be loved. Even better seeing those same kids in a couple of years, still having fun and enjoying themselves.
The greatest thing is that nobody is automatically "too old" to just be there and have fun (though we did informally require that they be able to hold a child as needed when someone needed some cuddling). Even our older deacons would serve about once every two months or so, just to be in with the kids and show them God's love.