Check in with your airline and get your boarding documents. Immigration facilities at Houston Intercontinental Airport are beyond airport security--and you won't be let past the security checkpoint with a boarding pass.
Present the immigration officer with your passport and boarding documents. Remove any hats or glasses, as he'll need to take a picture of you so the computer can check your biometric data, which includes facial features and your eyes, against the information stored in your passport file.
Take your passport when he's finished with it. Open it to your U.S. tourist visa, which will have a red "canceled" stamp on it. When you exit any international airport on a tourist visa and have no entries remaining, an immigration officer will always cancel it; there's no need to turn it in.