Like painting, drywalling is a very labor-intensive technique. In addition the drywall installer and taper has to be skilled because any imperfections will be picked up long after the painters have left. This is why a great emphasis should be placed on hiring the right drywall contractor for the job.
Drywalling is actually two separate jobs. The first part is the sheetrock installation which entails cutting, shaping, putting the panels into place and then fastening them. The second part includes taping the seams and then sealing both these and the screw heads with drywall compound. This latter process revolves around coating and sanding these surfaces until the walls and corners are smooth and you can’t tell where one sheet begins and the other ends.
If you take a look at a finished wall in any home it looks like a seamless flow of color which is only interrupted by the corners. And these looked like they have been hewed from a single block with a precision saw blade. Only your previous knowledge of building will tell you differently. However, the drywall job is only as good as the framework to which it is fastened.
A sheet of drywall is actually a dried slab of pressed gypsum with a tight skin of paper on each side. So besides the fragile bond of the gypsum itself only the paper holds this inner core together. This whole 4′ wide sheet, whether it is 8′, 10′ or 12′ long, is held onto the framework with either drywall screws or nails and the holding surface for these fasteners is just the thin, compressed paper. If the wall is bowed or warped at all the heads of these fasteners will work their way through the board as the sheet tries to retain the original attitude it had when manufactured.
This is the same for ceilings as well. Sometimes drywallers will add cardboard shims putting the ceiling on as it is hard for the framers to get 10 -12 joists to hang exactly the right height. Long boards like these have crowns and valleys that occur from the kiln drying process. Some drywallers will use a laser level to get this right while others will shim as they go along. Either way it is the skill of the installer that is important.
This can be accomplished through a variety of places like the internet, home building stores and word-of-mouth. Usually home building places are good because they know the credit history of all the contractors and can give you an idea of who is trustworthy. Web sites like HandyAmerican.com can provide you with detailed information about contractors rated and reviewed by your neighbors.