What does it mean to order a drink on its own, and how does it differ from drinks with ice?
The bar terms (neat, on the rocks, shaken or stirred) describe how the liquor gets into the glass, and ice changes almost everything.
Ordering a neat drink means receiving a couple of ounces of your chosen liquor, unmixed, unshaken, and without ice or soda water. It's a drink to be savored slowly, designed to let you appreciate the spirit as is.
The usual choices are whisky, bourbon, scotch, or brandy, although premium mezcals and tequilas are also served. The drink arrives at room temperature, typically in a lowball glass, a balloon glass, or a whiskey glass, without any garnish. Simply specify the quantity and type of drink.
Ordering a drink with ice means a cocktail or liquor served with ice. It's the typical way to prepare classics like the margarita or gin and tonic, although you can also order bourbon, tequila, or another spirit with ice to soften its flavor.
If the drink needs to be chilled, the bartender will shake or stir it with ice and then strain it before serving. Martinis, cosmopolitans, and gimlets are served without ice, although a margarita can be prepared the same way. If you prefer a slightly stronger drink, ask for it shaken rather than stirred, or vice versa.
"Straight" is synonymous with "neat," meaning without ice or mixing. Saying "straight up" is more confusing than helpful, so the clearest thing to do is ask for "neat" or "up."