We all detest them, but many of us have them. The stipple or popcorn ceiling. The recommendation is to remove the stippling to get the clean look of a drywalled ceiling but often times this just isn't an option. Time constraints & the possibility of opening a whole new can of worms, such as builders not priming before applying the offending stipple, are the two most often quoted reason for not eradicating stipple from a home.
If you want to freshen the ceiling with a coat of paint there are one or two steps you must follow first.
With a spray bottle, wet an area of ceiling. If the stipple absorbs the water after sitting for a few minutes (it will become soft to the touch) you will know the stipple has not been primed. In this case, proceed to step number 2. If the water does not get absorbed but remains on the surface of the stipple you've gotten the go ahead to skip step two and go straight to paint the ceiling.
If you've determined the stipple is absorbing the water you must prime the ceiling with an oil based primer before painting.
When priming and painting the ceiling make sure to use a high nap roller specifically for stipple ceilings and paint in 2 directions perpendicular to each other in order to cover all surfaces of the stipple.
When you calculate the amount of primer/paint you need...double it. There is a lot of surface to your stipple ceiling!
And here's the completed ceiling which I painted in Benjamin Moore's Titanium: