serializing objects to json with play.api.libs.json

I'm trying to serialize some relatively simple models into json. For example, I'd like to get the json representation of:

case class User(val id: Long, val firstName: String, val lastName: String, val email: Option[String]) {
    def this() = this(0, "","", Some(""))
}

Do i need to write my own Format[User] with the appropriate reads and writes methods or is there some other way? I've looked at https://github.com/playframework/Play20/wiki/Scalajson but I'm still a bit lost.