Four-poster beds are elegant and comfortable to sleep in. They give the feeling of the bed being separate from the rest of the room, with or without curtains surrounding the sleeping area. These are often for sale at most furniture stores and include directions for assembly, but if you get a bed without instructions, they are not hard to put together.
The most critical part of a poster bed -- or any bed, for that matter -- is the bed frame itself. Assemble it before you can put anything else on top of it, and it needs to be sturdy. First, put together the headboard and foot of the bed, attaching them to the bed posts (lower halves). The headboard is usually taller than the footboard, and often placed against the wall of the room.
When those pieces are assembled and in position, there are usually two long side slats you can install now. They run along the sides of the bed, and attach at the corners, usually using long screws through the head and foot of the bed, and bolts in the slat itself. On larger size beds -- full, queen or king -- there may also be a center slat, sometimes metal, that you should attach for extra support.
Many beds also have a series of slats used to keep the mattress and box spring from falling onto the floor. If there is also a frame to keep these slats in place, install it before putting them in.
The posts themselves are often designed to be optional, based on your choice. There should be slots on the four corner posts into which you can install the canopy posts, using the pegs on the bottoms of each post.
If you have a canopy frame as well, install this after the posts are all in place. These usually have notches that allow them to fit flat together on top of the bed, and screws that keep the frame in place. For best results when screwing the top into place, stand on a chair to reach these points.
If you are putting a curtain canopy on the bed, do so before screwing the canopy frame into place. Use regular curtains to do this, and slide them onto the canopy frame, pull the curtains to the middle, and screw the frame into place. You can use some basic curtain ties, or a decorative rope to tie the curtains out of the way when not in use.