Oh yes, christenings... well, you contact the priest at your local parish and discuss dates with him. It's the last day of every Sunday at ours. You meet up, talk thing over, arrange payment etc.
Everything else, like the function afterwards depends upon what you're after. We;ve booked a function room in a private club, caterers, ordered a cake, negotiated drinks prices and have just ordered invitations to be sent out asap. Entertainment will just be a bit of background music.