A: Practice. If you can, take the child to the ceremony location a week or two before the wedding (remember, it's a big day for him as well). You and your fiancé can do a mock ceremony, explaining what will happen and what he has to do—with kids, you don't want to spring any surprises at the last minute. Ask him to show you how well-behaved he can be as he demonstrates his walk down the aisle. Let him know that there will be lots of friends and family there who are looking forward to seeing him. Afterward, the three of you should go out to a celebratory lunch, where you give him a little gift. Tell him there'll be another gift coming his way if he behaves nicely on the wedding day. Some may call this bribery; we call it brilliant!