Everyone's stool is pushed in.

Bud Light beer everywhere.

You see anticlutch’s photo above the door.

I guess I'm going to be the party pooper who advises staying the hell OUT of bars of any sort at all times. If you want to drink get some buddies you know and trust together at someone's house.

Yell "did you see a little boy in here?" and see how they react. They can't resist a new recruit.

Probably from paying attention to the voices of men talking. The absurd amounts of lispy feminine-like chatter will probably give it away.

Yell faggot, if anyone takes exception it's a gay bar.

Go to the restroom, look at the art. If the men's restroom has "artsy" pictures of dudes with abs and the women's has propaganda about the patriarchy...now you know.

There is a bouncer monitoring the open, male-restroom door.

The nigger with his balls out besides the jukebox.

Instead of bikini clad women posters, there are probably men in some kind of village people looking outfit I suppose. The rainbow flags or bar back dildoes would probably be another give away, assuming they plaster those all over the place like they do in the white hetro places.