It always pays to take a look around before you sit down at a place.
Take the woman in the table for example-sitting alone, looking well and truly pissed off at everything and everyone. The way she tenses up, squares her shoulders, bristles at anyone who so much as looks at her. A woman looking for a fight, and judging by the amount she's drinking, apt to find one sooner or later-most people who don't want to bothered take a seat in the corners, back to the wall, in a defensive huddle. She's right in the middle of the room, suggesting she wouldn't care if someone did-might even prefer it.
Not much to look at, and though she has her perks, you'd be a madman to try and chat her up right at the moment. Lean, fit, and ordinary-skinny as a rail, short as a fence post, and not much of a body in either direction, on the X, Y or Z axis. Fairly healthy skin, her face plain and unmarked by age (you'd put her far younger than she looks, honestly), and vaguely Germanic-facial features square and flat like a box, with a tough jaw and prominent cheekbones.
And, for her more obvious charms-the woman is armed, with a government issue baton, and two pistols securely strapped at her slender waist. A sensible rig for carrying openly, yet not for a wanna-be gunslingers draw, a criminal, or a soldier. It's easy to peg her as professional security, maybe a cop or a MP-the way she cases the room, the weapons subtle and discreet, the sort who draws weapons only when she needs them. The more observant of you might notice one of her pistols is pretty clearly of the non-lethal variety (the distinctive bulged holster fits a standard restraint carbine), which pretty much confirms it. Someone who has trained to kill, but only as a last resort. It's pretty clear she's not on the clock right now, though.
The woman merely continues her slow descent into angry oblivion as we watch, occasionally fooling with a shiny keyfob to some sort of motor vehicle in her left hand, seeming restless and lost.