Remove all furniture from the room. Cover the floor with dropcloths and secure them to the baseboards with painter's tape.
Set up the scaffolding in one corner of the room. Make sure it's high enough to allow easy access to the ceiling.
Climb up the scaffolding and apply painter's tape to the joints between the walls and the ceilings. Move the scaffolding around as you work to get all of the walls.
Cut in with the paint, using a small edge roller. Start in the far corner of the room. If necessary, use a brush to get into the edges, but roll this paint out to remove your brushstrokes.
Paint the rest of the ceiling immediately. If you allow your cut in marks to dry before painting the rest of the ceiling, this will leave what is called a "hat band" or "picture frame" effect where you have a visibly darker line around the edges of the ceiling.