I assume you have completed all your Preparation and you have all your Painting Tools and materials ready to go.
Ceilings:
If you are going to paint the walls no need to worry about protecting them but if you are painting the ceiling only you should mask off the walls with some lightweight plastic drop cloths.
Do you have Popcorn Ceilings?
If so you need to read this Painting Popcorn Ceilings
Start by "cutting in" around the edges, light fixtures etc. using a 3"- 4" paint brush. If you are painting the walls a little overlap onto the wall is OK but if not use a small handheld shield to protect the wall. There are quite a few styles available at your paint store or home bldg center.
Once your cut in work is completed you can begin rolling. The thickness of the roller cover depends on how textured your ceiling is. A 1/2" cover is fine for smooth surfaces but rough textures like "popcorn" require a thicker 3/4" thick nap.
If you have a roller pan, throw it in the trash! As I stated in the Tools section, I am convinced these were invented by carpet sales people so they can sell you new carpet when you, 1. step backward into the pan, or 2. when it falls off the ladder because you attached it with the flimsy hooks that are provided.
Get yourself an empty 5 gallon pail and a "roller grid" a nifty wire like ramp that attaches to the bucket rim and is used to remove excess paint (appx $3.00)
Since we have to mix all our paint before starting to insure the same color thruout,the 5 gallon pail is ideal and you will have a lot less chance of spilling your paint.
You can use a small 1 gallon workpot with an inch or two of paint for your cutting in.
Attach a 4' or so wood handle to your roller frame, it screws right in so you can paint from the floor, run your roller down into the paint and roll it over the grid to distribute the paint evenly. This also removes the excess paint and you will find that you have very little dripping.
Work in 4' sections or so applying the paint in a "W" pattern then going back over it to distribute it evenly.
Its a good idea on ceilings to roll in the direction of the window across from the entry door. This helps to hide any roller lines which may be introduced.
Painting Walls: Basically the procedure is the same. You will want to "cut in" at the top where the wall meets the ceiling, around all your door, window and baseboard trim, and around outlets, switches etc.
Its a good idea to do one wall at a time, cover the floor, cut in and then roll. This way the paint from the cut in is still wet and there is less chance of a color miss match between brush and roller work.
Always keep a bucket of water handy so that you can clean up any spills or splatters while they are still wet.
Of course use paint thinner if using oil base paint.
Now that the walls and ceilings are complete, lets move on to
painting the Trim
Add Insulation to your Paint !
Thats right, thanks to newly released NASA technology you can now Insulate while you Paint.