In any business a huge crunch of the sales will come from referrals, but in a wedding business this is even more crucial. When you get a client/customer through a referral they are already motivated to buy from you which makes your sale much easier.
Alexandra Levit writes about the importance in creating a system for gaining referrals in her blog. She encourages people to make it easier on your customers to refer people to you. While gaining referrals from other businesses works best by paying them a percentage of the sale referrals from other clients need to be encouraged to refer others through a bonus deal enabling them to get something that they otherwise would not be able to get.