Surface treatment: A shiny granite may best suit a formal kitchen, but in a more rustic setting honed is usually a better choice. Some stones, such as soapstone and slate, can't be polished; a matte, honed finish is your only choice. Keep in mind that the surface treatment can also affect maintenance. Polished granite, for example, is easier to keep up because it resists stains and water marks better than honed. But on softer stones, such as marble or limestone, a honed finish is easier because you can use a scrubber sponge or a light abrasive cleaner such as Soft Scrub without worrying about scratches.
Thickness: Stone slabs come in two standard thicknesses: about ¾ inch (2 centimeters) and about 1¼ inch (3 centimeters). Thicker stone has a greater visual heft that's generally preferred in kitchens. To get the look for less, ask your installer to glue or "laminate" a strip of stone to the edge of a ¾-inch slab. In a quality job, these edge strips will be cut from the same slab and the transition will look seamless.
Pro Tip: "Before you buy a slab, bring home a few samples and look at them in your kitchen at various times during the day. A stone's appearance changes dramatically depending on lighting conditions." —Carole Freehauf, This Old House interior designer