Texans use the word "y'all" a lot. You'll hear it in pretty much any type of conversation, and you'll likely incorporate it into your vocabulary before heading home. (It really is a useful word, and it sounds so nice—at least when Texans say it.) There are a few other sayings and pronunciations that are unique to the Lone Star State:
"He's all hat and no cattle": Used to describe someone who is all talk and no action.
"This ain't my first rodeo": I wasn't born yesterday.
"You can put your boots in the oven, but that don't make them biscuits": Say what you want, but that doesn't make it true.
"We've howdied, but we ain't shook yet": We've made a brief acquaintance, but have not been formally introduced.
Burnet: "Burn-it"
Pedernales: "Pur-dah-nallis"
Guadalupe: "Gwaa-dah-loop"
Manchaca: "Man-shack"
San Felipe: "San Fill-a-pee"