Instructions

• STEP 1: Convert a rectangular table - perhaps a sofa table or a dining table - into a desk by installing a keyboard tray under the top. You can usually push a two-drawer file cabinet or a roll-around drawer storage unit under the table top to keep the storage close by and the office footprint small.
• STEP 2: Buy a rectangular prefabricated table top - sold at home centers - or a sheet of plywood (cut to desktop size; finish the edges with self-stick strips of wood or plastic veneer). Put a file cabinet on each side of the table top and, if you have a computer and want the keyboard at proper height, install a keyboard tray on the underside of the desktop.
• STEP 3: Opt for a sawhorse-and-table top (or plywood-topped) desk. Screw the desktop to the tops of the sawhorses, which are placed at opposite ends of the desk.

Tips & Warnings

• Paint your desk a bright, fun color for a whimsical look or go with black for a high-tech look.
• Substitute a flat door (you may want to cut it down) for a desktop perched on file cabinets or sawhorses.
• Look for keyboard trays and roll-around drawer storage units at office supply stores. Roll-around drawer storage units (usually the open-wire styles) also are sold with closet/pantry organizer gear at home centers, and organization/storage speciality stores.

Source:http://www.ehow.com/how_13735_make-inexpensive-desk.html