Aim to run it as professionally as you can. Don't cut the tournament short in order to preach to people - by cutting the tournament, you will almost certainly already have lost their attention. Don't in any way give the impression that the sport is unimportant and only a means to the end of preaching to them. Christian content The prize-giving ceremony at the end provides an excellent opportunity for some Christian content. Depending on your purpose, this can be either a gospel presentation or a more low-key invitation to the next event.
Materials Give everyone a gift when they leave.
Follow up If possible make the competition part of a programme of events. Have some future event to invite people to.