"Giving away samples. If we spend $2,000 to give out samples and [discount] cards at a thousand-person event, 10 to 15 percent of attendees will visit us, and at least 25 percent of them will be new customers. We spend around $2,000, but we get 25 new customers over two years, and each generates about $1,500 of value."

--Kaleb Harrell, co-founder, Hawkers Asian Street Fare (food and beverage)

No. 1,247 2016 Inc. 5000 rank | 310% 3-year growth | $6.9 million 2015 revenue

"We can bring on new brokers to find landlords who want us to perform construction and manage their properties. These brokers get a commission--10 percent of the profit for construction, variable for management. But it's low compared with the business they bring in and the cost for us to hire a marketing person full time to do what they do."

--Drew Millard, founder, 33 Realty (real estate)

No. 507 2016 Inc. 5000 rank | 749% 3-year growth | $11.9 million 2015 revenue

"Do a deep analysis of your sales or your leads using your key metrics, broken down by marketing channel: organic, referral, advertising, online ads, social, press, etc. One or two of them will vastly outperform the others. If you want to grow quickly and cheaply, double down on the channels that are working. Then determine your conversion rate--how many visits from customers turn into sales? Most companies have a 1 or 2 percent conversion rate. Pick something that could be a change agent: store layout, or the wording on your website or in your marketing materials. Try different versions and see which one gets more conversions."

--Paul Weinert, founder, Graybox (advertising and marketing)

No. 370 2016 Inc. 5000 rank | 1,038% 3-year growth | $2.1 million 2015 revenue

"Expanding our email list. We pick a high-traffic webpage, like our ring-size chart, and put a question on it, like 'What does your stone shape say about your personality? Click to reveal.' Customers enter an email address to find out. We can get several hundred emails fast."

--Elena Castaneda, founder and CEO, Bling Jewelry (online retail)

No. 3,192 2016 Inc. 5000 rank | 105% 3-year growth | $14.9 million 2015 revenue

"Customer referrals. Many business owners forget about that. The best time to acquire referrals from a customer is right after we engage in a deal, because that's when all parties are positive. Referred customers bring in better business than those from any other channel. It's cost effective. It's low-hanging fruit."