Andie, First, be sure the glides you select will carry the weight loads you require. Next,purchase your glides, or get the specifications literature on them; this will tell you how much space they require (and the weight specs). They also normally give you specifications for how much clearance is needed on back, sides and top, too. Also look at how they attach; if they attach to the center of the drawer bottom, you'll want to use at least 1/4", maybe 3/8" material for the drawer bottom, so that the screws for the track don't stick up through the bottoms. If these are larger drawers which will hold heavier amounts, you may even wish to use use 1/2".
Use the specifications to determine the actual drawer sizes (frame width/height minus the clearances specified). Most important, be sure they are square, and definitely use wood glue when joining sides and bottoms.
How did you plan to build them, and with what materials?