Go to Keller's Drive-In on Northwest Highway on a Saturday around lunch time. Those burgers combined with classic cars, motorcycles and old lady waitresses are a real treasure. Take a picture in your mind of a poppy seed bun in your hand, and a bottle of beer on your dash back-lit by the Texas sun. The image will last far longer than what ever semi-important thing you recently captured on Instagram.
You should eat tacos -- as many as you can handle and then a few dozen more. They're cheap, which will help offset the cost of some of the more expensive restaurants you'll want to dine in before you leave, and they're delicious, too. Tacos, like the ones served at La Banqueta, Bachman Tacos and Grill, and Los Torres Tacos will leave with with a warm glow, and if you're feeling adventurous, wrapping lamb in freshly made tortillas at Barbacoa Estilo Hidalgo is memory-worthy as well.