Went to the State Fair on opening day.
You can sign up for a promo code at bigtex.com for $10 admission on Tuesdays and Thursdays. Also, if you go on a Wednesday, you can donate 5 canned food items per person for $5 admission. On Opening Day, you could donate 2 jars of peanut butter for $10 admission. There are also admission coupons at McDonald's.
Fletcher's Corny Dogs is a must eat. The Original Corny Dog, The Jalapeno & Cheese Corny Dog, and The Cheesy Pup (American cheese on a stick dipped in corn dog batter and fried) are excellent. Go to one of the Fletcher's stands on the Midway for a short line. The ones by Big Tex and the Cotton Bowl have long lines. Lots of other good concessions as well.
Big Tex is a must for a group picture/selfie.
Texas Auto Show is good to see new cars and trucks. The only luxury brands were a few Acuras and the Mercedes Sprinter vans.
Chevrolet Ride & Drive is free and fun to drive the Corvette, Camaro, and other vehicles through a course.
The Go Texan Pavilion has made in Texas food products for sale and free samples.
The Hall of State always has good exhibits. This year they have an Alamo exhibit with a huge model of the Alamo battlefield, and a Mav's Vault exhibit with historical items from the Dallas Mavericks including the 2011 NBA Finals trophy and a Lego replica of the AAC.
The Creative Arts building has the Butter Sculpture and the arts and crafts contest winners.
The Women's Building has a good Dia De Los Muertos exhibit.
The Starlight Parade is good if you are there at night 7:15pm. We saw the Opening Day parade at 12pm.