A few months ago I added a "coupon code" referral system that makes every customer an affiliate. When the customer finishes the online education course they get a 7 digit number that to give out to their friends via Yelp, Facebook, and other social media.
When their friend, with the coupon code now, takes the course it tracks back to the referring customers account, giving a commission. This encourage new customers to use the referral code (by a discount) and gives the giver the knowledge that the referral will put in the number so the commission gets tracked.
This leads me to Yelp, as our customers started leaving reviews and their referral codes on Yelp suddenly conversions from Yelp took off and Yelp became the 3rd most provider of referrals (after Google Adwords, Google Organic). Now we have over 100 yelp reviews which really stands out when found through a Google search, and with so many reviews the business is always listed above all of the others.
Yelp has a great deal of visitor traffic and when you harness Yelp by fully completing your profile and any
encouragement you can provide to customers to leave reviews you will certainly see a dramatic increase in sales.