The centerpiece of the show, is, of course, the brewery tour. The tour costs $7, and crucially includes a souvenir glass and tokens, which you can exchange for four free beer samples. Texas state law does not allow the brewery to sell its beer direct to visitors, so this is the only way to sample Saint Arnold's beer while you're on the premises.
The heart of the brewery is a large beer hall, where visitors are encouraged to bring picnic lunches or snacks. Repeat visitors are known to skip the tour and simply use their sample-filled souvenir glass to wash down their meal. Each sample is 8 ounces, which means you can have as much as 32 ounces of beer, but that's really the limit: you're not allowed to purchase another "tour" by entering more than once.
Saint Arnold also hosts other events throughout the year, including pub crawls (a great way to get to know Houston's beer scene), a beard growing contest (called the Donegal competition), Oktoberfest celebrations, beer and cheese tastings, and so on. You can sign up for the brewery's newsletter to see what's on during your Houston stay, although you'll find more up-to-date information on Saint Arnold's Facebook page.