Decide whether you want a side-mount, or under mount slides. The amount of space between your drawer box and the cabinet opening will affect your decision.
Side-mount slides are sold in pairs or sets, with a slide attaching to each side of the drawer. Available with either a ball-bearing or roller mechanism. Require clearance – usually 1/2" – between the drawer slides and the sides of the cabinet opening.
Under mount drawer slides are ball-bearing slides that are sold in pairs. They mount to the sides of the cabinet and connect to locking devices attached to the underside of the drawer. Not visible when the drawer is open, making them a good choice if you want to highlight your cabinetry. Require less clearance between the drawer sides and the cabinet opening (usually 3/16" to 1/4" per side). Require specific clearance at top and bottom of cabinet opening; drawer sides typically can be no more than 5/8" thick. Space from underside of drawer bottom to bottom of drawer sides must be 1/2".