The four key elements of a quality billiard table are genuine diamond-honed slate, a solid frame/cabinet with metal-to-metal construction, top rails with a catalyzed varnish finish, and strong legs/support.
A quality table should utilize diamond honed slate (to insure flatness) that is a minimum of 7/8" thick. The slate should be "oversized," meaning that it fully extends underneth the top rails to provide support for any weight applied to the top rails (such as player leaning to make a shot). Higher end tables will incorporate a backed slate (wood backing) that allows our installers to stretch the cloth tighter providing a better playing surface.
The cabinet provides a decorative or ornate cover for the frame which provides the foundation for your playing surface (the slate). Quality billiard tables utilize metal to metal construction at the joints to insure proper alignment and prevent overtightening.
The top rails are the most abused part of the billiard table. They are constantly exposed to balls or cues being dropped on them, belt buckles being scraped across them and numberous other events that would damage wood with an ordinary varnish finish. Some manufacturers and models incorporate a catalyzed varnish finish that is baked into the wood, so while your top rails will get character marks (small dings) the finish will not chip or flake.
The legs provide the support for the entire table. Legs are very important considering a billiard table typically weighs in excess of 650 pounds. Legs can come in a number of different style, but should provide ample support for distributing the weight of the table, frame and slate evenly.