Use a wedding budget calculator (you can find them online) to figure out how much should be spent on each expense. Then, start saving for the big day.
Twelve to 18 months in advance of the wedding day, figure out as accurately as you can what it's going to cost you. Divide the total by the number of paychecks you'll get before then and start automatically shuttling that much money into savings. You can even open a separate savings account if it'll help you keep your fingers off!