If you are not a master woodworker, but want to turn a regular bed into a canopy bed, there is an incredibly simple way to do it.
First decide where you want the canopy to drape and whether or not you want full side curtains. There are three potential methods listed in the steps below that can be used alone or mixed and matched.
For a simple look without the side curtains, screw four drapery hooks into the ceiling above the four corners of the bed. Drape sheer curtains or fabric over the hooks, leaving one end to fall straight down over the corner of the bed to the floor, attaching the other end to a different hook over another corner of the bed, allowing the fabric to drape and fall however you desire. Add more hooks along the way to make up for shorter fabric or to create a different look.
For a canopy look with full surrounding curtains, attach drapery rods to the ceiling parallel to the edges of the bed. Hang curtains on the rods as desired. You can combine the two methods, using the hook and drape idea on the outside of the curtain rods to finish off the look.
A great idea for a circus tent or a princess bed is to attach fabric to a needlework hoop or other circle of any size you desire. Start by gathering the fabric to a point. Tie or sew this end together if desired and decorate with ribbons or bows. Then glue fabric to the needlework hoop about one or two feet from the gather point. Drape and pleat fabric as desired. Once complete, simply hang one hook from the ceiling and attach fabric at the gathered end.