on the ceiling north and south across the ceiling joists, not along the ceiling joists. To many weekend warriors run the dry wall in the same direction as the ceiling joists, this is a no no and will sag within one to two years.
Always use 5/8th's on ALL CEILINGS EVEN IN GARAGES, 5/8th's is much stronger and firm then 1/2 drywall!
Use screws and not nails to hang your drywall, this goes for the walls also!
Go to a outlet that only sells sheet rock to builder's and drywallers, ask them any question about the sheet rock and drywall screws, 5 minutes talking to one of those guys will clear everything up for you Jim and if you have the budget you may want to think about having it hung for you, they will make short work of that kitchen. Hanging sheet rock is hard hard work even for hanger's that do it everyday, for someone that doesn't do it for a living or have the right tools it can and probably will be a nightmare.
You have to look at it this way Jim, this is probably your last kitchen, your dream kitchen, at least let a pro get you started in the right direction hanging the sheet rock so it last for the next 50 years, now the finishing work is a whole other story, one step at a time
The sheet rock outlet can give you the name and number of drywall hanger's looking for side work and let me tell ya Jim, now is the time to grab these guys because they are all looking for work because their is no building going on now so you can wheel and deal with them, that's if you have the extra cash on hand.
Good luck Jim, feel free to ask any question and I will do my best to answer it
