My sister-in-law gushes about wooden cutlery, a pretty cupcake box and half-eaten cookie wrapped in a delicate paper bag with "Magnolia" stamped on it. She and her husband brought this stuff back from a business trip to Austin, Texas, where they drove 100 miles--nearly two hours one way--to stand in line in the 105-degree heat to get pastries at Silos Baking Co. and walk through Chip and Joanna Gaines' retail marketplace in Waco.

The Gaineses--famous for renovating houses in the Waco area on their HGTV show "Fixer Upper"--have transformed Waco into a travel destination that attracted nearly 2 million visits to its major attractions last year, up from 660,000 in 2015. Indeed, the couple has figured out how to build an unstoppable brand. Here's what they've done right.

1. People love a brand with a sense of humor.

Chip's goofy antics and quips play a big part in what people like about the show. It turns out that smiling and laughing release the feel-good neurotransmitters dopamine, endorphins and serotonin which make people feel happy and lower heart rate and blood pressure. When a brand can elicit this response, it makes people feel connected as if they're hanging out with friends.

2. They invest heavily in social media.

Joanna topped the "TV Personalities on Social Media Chart" published by The Hollywood Reporter in June, with Chip following on her heels at seventh place. While they're on all the major platforms with millions of followers between them, Chip's Twitter feed feels authentic and Joanna's presence on Instagram consistently promotes their show.

3. No one dislikes a brand that's family-friendly.

Try to think of the opposite. While a show such as South Park may receive accolades for pushing boundaries and raising eyebrows, it's also going to have some haters. Not so with Fixer Upper--Chip and Joanna give their kids cameo appearances on every single show and their family life is a big part of what makes their brand so likeable.

4. They continually build on their success.

Their brand has expanded beyond the show to a retail and dining destination at the Silos in Waco and an ecommerce site where designophiles can purchase things like candleholders, vases and "Joanna's favorite sachel" (the latter runs for $220). A realty company also sits under the Magnolia umbrella as do two vacation rental properties. About that--Magnolia House goes for $695 to $995 a night and is sold out for the rest of the year. Do the math and it's easy to see why the couple recently announced they will soon be taking reservations for a second property called Hillcrest Estate in Waco, which sleeps 12.