Protect the furnishings. Remove all the small items from the dressers by either putting them in the drawers or putting them in a box. Move all the furniture away from the walls to the center of the room, and cover everything with a drop cloth. Use this opportunity to vacuum the dust along the base boards and in the corners of the room.
Start with the trim. Paint the trim first, using a two-inch brush with an angled tip. The angled tip makes it easier to get into the corners and paint the smaller surfaces. Start in one corner of the room and work your way around in a clockwise direction so that you don't miss any spots. Paint the trim around the windows, the baseboard and the crown molding, if you have one. Also paint the walls in the corners of the room where the roller won't reach.
Roll the walls. Start in the same place where you started painting the trim and work around the room in the same direction. Cover the floor with a drop cloth because paint tends to splatter from the roller. Roll in long motions from the top of the wall all the way to the bottom to avoid leaving roller marks.
Add a second coat of paint after the first has dried thoroughly. Start with the trim, as you did for the first coat. This time, work your way around the room in the opposite direction, so you have a different perspective and can see spots that were missed the first time.
Reassemble the room. Let the paint dry overnight before putting the furniture back.