There is a volume knob for the live bands that play atop LSA. It's location is in the men's restroom of The Chestnut Tree underneath the sink.
Midway Mart has a phone list of people that they will text when they get cool/fancy orders in. Also, their Twitter account does pretty much the same thing.
Both Cafe Brazil and Tortilleria La Sabrocita are open 24 hours on Fridays and Saturdays.
Broken Nose Supply has lots of awesome art supplies and knowledge if you don't feel like dealing with Voertman's.
The A-train and DCTA often give free rides via passwords on their Twitter feed. Especially around special events or festivals, great way to ride the rails for FREE now that you can take it all the way to DFW or straight down to Love Field.
Karaoke at Crossroads Bar and Crossroads Bar in general.
The new Hoochies Oyster House has a secret menu item: The Baton Rouge (a former favorite), an open-faced blackened catfish po boy topped with cole slaw. And you can still get a $1 "train beer" when the whistle blows from the nearby tracks. And if you ain't slurping up their oysters on 25 cent special, you're doing it wrong.
1670am exists.
You can get local meat and dairy all week long (not just during the Community Market) at Earthwise.
UNT has star parties on the first Saturday of every month in which you can check out telescopes and pretend to be an astronomer. Plan ahead here.
The north branch of the Denton Public Library has a 3D printer that is available to all if you just take a free class on a Monday evening.
Not really a secret, but there is stuff in Denton beyond the square and Fry St. Venture out and explore.
Meador Nursery on 377 is pretty awesome and has all sorts of cool plants. You know, if you're into plants and stuff (we are).
Although another Dan is a far more famous Denton hang-out, Dan's Meat & Produce sells a shockingly diverse variety of specialty cheese and meats like grass-fed local beef, bison, duck, andouille sausage, lamb, and regular closeout specials that are competitive with the Kroger or Whole Foods fare of lesser quality. And OMG their thick-cut back bacon!
Wine2 has a new super-secret covered back patio, perfect for lazy loitering with a cold beverage or enjoying their secret "Bottle and a Blanket" service for picnics on the lovely Courthouse grounds. Waitasec, don't print this one.
UNT builds buildings based on the Hermetic Code or something. We dunno. Read this.
You can get mini cinnamon rolls at Royal's Bagels if you have a large order.
We were going to say Taipei Railroad as the best secret Taiwanese restaurant, but it has since closed. So instead, we'll just say this - if you find a good restaurant off the beaten path, share it with others and go often. We've lost too many good restaurants lately (like Taco Lady).
The Denton Firefighters Museum is free and open to the public. More here.
Willie Nelson is actually dead and buried in between the floors at LSA.
Becoming a member of the Denton Main Street Association gets you a discount card for a bunch of participating local business. They also host a pretty cool Arts Antiques & Autos Show in September.
The bones buried in John B. Denton may very well not be John B. Denton. Seriously, though, this time. Use that in your next, "Did you know..." conversation.
Want to partake in the vicious locally-roasted coffee wars? Shop for your roast next to the local music section of Recycled Books. They have pretty much all of the local roasters on their shelves. No kidding.