When beginning to install the sheetrock, you usually begin with the ceilings; but understanding "seams" can make all the difference in the world in achieving a quality job from start to finish.  The first rule is to keep the factory recess, called the "flat" because at the factory it is compressed and made "flatter" than the rest of the sheet.  The next rule is to try to stagger your end seams.  It is usually easier to hide the end seams with the finishing work when they are not all in a row across the ceiling. 

But don't forget a key ingredient:  GLUE!  On the ceilings I like to leave a heavy bead all across the framing as I hang each sheet.  If you skimp on the glue, you force the nails and/or screws to do all the holding on their own.  Bad idea!  I have seen whole ceilings collapse in people's homes after 15 - 20 years because the moisture from the attic was able to weaken the sheetrock around the nails and screws.  Once the first sheet started to fall, a ripple effect took place and the whole ceiling plummetted.  The sheetrock had only token amounts of glue on it, and in many cases, none at all.

Another reason to glue generously is to hold all the parts of the seams tight.  No one likes to have the seams start cracking and popping a year or two after the work is done.  While sometimes the framing itself is to blame, many times the seams develop problems because the drywall was never glued properly. 

It is very common in new house contruction for drywall installers to skimp on the glue and just put trace amounts across each ceiling joist.  I have encountered some installers who know how to use a little here and there, then take the surplus to return to the store for cash, or simply sell through their own channels.  Since very few people are on the job while the drywall is being installed, this is a very easy way to put a few dollars in the back pocket.  Unfortunately, the homeowner will pay the ultimate price years down the road.

So when you are doing your own project, use a healthy amount of glue.  Don't worry if a little gets on the face of the sheetrock.  Once it dries, it will scrape off easily.  You'll be glad for the investment years down the road.

John