Tape off the area around the ceiling and floorboards so you don't get paint on them.
Press the paint roller into the paint tray so it is covered in paint, but not dripping.
Apply paint to the wall by pressing it with light pressure against the bottom left side of the wall and moving it at a very slight left angle.
Press the roller straight down so the right edge of the roller is overlapping slightly with the left edge of the paint that is already on the wall. This overlapping will prevent the edges from drying separately, which can cause streaking.
Continue until the roller runs out of paint, or the paint starts to look uneven.
Roll the roller over the area you just painted. Use the same motions, and apply very light pressure. This will help create a uniform texture.
Continue working around the room. Do not let one strip of paint dry before you are able to place another one next to it. This will minimize streaking.
Dip a paintbrush into the paint, and paint the area around the ceiling and floor. Use long, uniform brush strokes, so the paint appears even.