Erin Condren knew her artistic day planners might not leap out at online shoppers, so she asked her regular customers for a favor--buy extras and give them to pals. "I thought, 'If I can just get this product into more hands, they will share it with friends,' " says Condren.

The approach worked.

Today, 12 years after launch, Condren's eponymous company, based in Hawthorne, California, has a formal customer-referral program that generated 24 percent of its $40 million in 2015 sales. Referring customers get $10 off a future purchase and referred customers get a $10 discount. Referrals may seem old-school, but Nielsen's 2015 Global Trust in Advertising study found that 83 percent of consumers take action--investigate a brand or buy something--on recom­mendations from people they know. Use these tips to mine gold from customers' real-life social networks.

Make your customers big shots

Your customers don't want to be salespeople, says Will Fraser, co-founder and CEO of referral-program platform Referral SaaSquatch--they want to be influencers. "Greed [for a reward] works to a point, but what really motivates people is gaining social capital," says Fraser. "The value you're really giving me is that I [as the referrer] have the ability to look like an insider and give a friend or colleague an offer as a VIP customer." With that in mind, give rewards to both referrers and those referred. Ztylus, a Houston-based maker of cell-phone camera cases and lenses, gives an initial 25 percent discount to referred customers and a 10 percent cash reward to referrers. The company gets 10 percent of total sales from referrals.

Size doesn't matter (much)

Companies have had success with simple cash payouts, percentage discounts, and less conventional rewards, but one surprising fact holds true: Small rewards perform as well as large ones. Luggage maker Trunkster used to offer referrers $30 off, but it saw no decrease in referrals when it lowered that to $20. The most important thing is to keep the offer simple. "You want to make your reward easy to understand for the consumers so it entices them," says Trunkster co-founder Gaston Blanchet. To really catch the customer's eye, go beyond just discounts. Fraser says you should offer free product whenever possible. "If you're a stock trading app," he says, "what's going to work there is credit to trade with."

Look out for scammers

Unfortunately, many people are out to scam referral programs. To collect the reward, some buy merchandise and then return it, refer imaginary people, or even forge coupons. To deter them, give rewards only when the referred customer buys something, not just for inquiries. Put limits on every aspect of the referral. At first, Condren didn't limit how much credit her customers could accumulate, and now a few have more than $10,000 worth. At Pavlok, which markets an electronic bracelet that helps break bad habits, CEO Maneesh Sethi is revising the company's six-month return policy to prevent buyers from collecting rewards and then returning the products. "We screen for people with massive amounts of referrals," he says.

Pay it forward: kooky kickbacks

When it comes to rewards for referrals, it often pays to go beyond the typical discount or cash payout. "If you can give them something cool, they're going to remember that," says Stewart Phillips, co-owner of the referral-program platform InviteBox. Referral company execs dish on the most unusual offers they've seen.

"There's one startup selling weed accessories online. I'm pretty sure its offer was 'Get $4.20 for every bud you refer.' " --Manish Goyal, CEO, Friendbuy

"We've run campaigns that offer charity donations--'If you refer a friend when you buy a pair of shoes, we'll donate $10 to the charity of your choice.' We've seen tuition credit in the education sector. We've seen VIP invites: 'Refer a friend and get invited to a special prelaunch opening.' " --Will Fraser, co-founder and CEO, Referral SaaSquatch

"We had one customer who gave a pizza from Chicago--a frozen pizza. They put it on dry ice and sent it wherever you wanted in the U.S." --Stewart Phillips