Dark is in. American semi- and bittersweet chocolate sales have shot up by 40 percent in the last two years. And, though it seems like every label out there boasts cacao percentages to grab buyers' attention, cacao mass percentage is just one piece of the chocolate puzzle. Choose the best chocolate fix using these three categories.

Cacao percentage
Dark chocolates balance the flavors of cacao solids (combined cocoa bean and cocoa butter) with precise amounts of sugar, vanilla, and milk—a higher percentage indicates a stronger cacao flavor. But more isn't necessarily better: A bar containing more than 85 percent cacao can taste too bitter. Most people prefer chocolates in the 50 percent to 75 percent range. Indulge: Chocolove's new Chilies and Cherries 55% Dark Chocolate Bar or Scharffen Berger's delicately complex 70% Bittersweet.

Origin
Just like wine grapes, cocoa beans have subtle flavors that vary depending on genetic stock and where they're grown. While beans from Madagascar have a citruslike tanginess, Ecuadorian arriba cacao is nutty and spicy. "Single origin" denotes beans from an individual farm. Indulge: E. Guittard's Ambanja from Madagascar or Dagoba's Los Rios Ecuador Single Origin bar.

Organic & Fair Trade
You can gauge a chocolate company's ethics by what's on its labels. Organic certified means that cacao was farmed using Earth-friendly methods, and fair-trade certified signifies that producers were paid fair wages. To qualify for both certifications, companies must satisfy rigorous criteria. Indulge: Theo 3400 Phinney Coffee Dark Chocolate and Green & Black's Maya Gold bar—both are organic and fair trade.