Get your client on-board to give referrals. Most sellers wait until after the sale has been completed before they bring up the idea of referrals. Bad idea.
Source: Sales consultant/author Paul McCord
Most clients need time to get comfortable with the idea of giving referrals, so bring up referrals early in the relationship. Don't ask for referrals; just let your client know that your business is built on referrals and then drop referral seeds as the sale progresses.
Since your prospects and clients aren't stupid, if they hear you mention referrals often in a casual manner, they'll get the impression referrals are important to you and they will be expecting you to ask for them at some point.