Learn the terms. The first theatrical stagehands were sailors, and many of the rigging terms (such as "rigging" itself) were adapted from 17th-century sailing ships. Ropes are attached to "pin rails" like the ones that lined the decks of the great sailing ships using "belaying" or holding "pins." A stage that uses ropes and belaying pins to "fly" scenery is called a "hemp house." The whole effect is that of a ship where scenery and drapes, like sails, are "flown" "in and out" of the scene, like sail management on a large ship.
Picture the structure. Drapes, lighting and scenery are suspended on "battens," long poles that hold them (like sails). Battens are suspended by ropes or cables through a system of pulleys on the ceiling of the stage. The "lines" travel up, across tracks and down on one side of the stage. They are secured on a "pin rail" with long wooden pins, or with locks that control another system of weights and pulleys. This system, called "counterweights," improves the mechanical advantage and allows pieces to be flown in and out with less effort. Professional theaters prefer motorized systems to replace counterweights and "hemp houses." The concept remains the same, though, requiring a ceiling at least twice the height of the stage opening (or "proscenium") to accommodate the flying pieces.
Conquer the engineering. The stage "loft"---the area above the stage---must be outfitted with sufficient support to carry the weight of scenery and draperies as they are pulled up or drop down, sometimes very quickly. Most lofts contain "catwalks," built on I-beams that carry the rigging equipment. Loft, head and mule blocks, clips and other hardware that guide the rope or cable through the tracks must be the right size and construction to avoid tangling (fouling) or excessive wear on the rope or cable. In many small theaters, certain drapes are fixed, their battens hanging on chains or cables; but in most large houses, all of the drapes, including the Main, can be flown. Side drapes (called "legs") may be fixed or flown. Only one batten is mounted in front of the Main drape---the fire curtain. It will have a mechanism that will drop it immediately, because the proscenium can act as a chimney out into the house if a fire starts in the confined stage area.
Plan what you want to fly. If you plan to fly only a few leg drapes and some set flats, your plan will be much simpler than a stage with a cyclorama, scrim and special effects. Shows with numerous, spectacular scenes require more complex rigging than shows with simple unit sets. The rigging that you install---and which the structure of your stage can support---will limit your choice of the type of shows you can produce.
Consult with several professionals with theatrical experience before building, and buy the best you can afford. Safety and predictability are your most important considerations.