First, purchase all of your painting materials. If you do not purchase anything in advance, you'll likely start painting without that item, and be unhappy about your oversight later.
Open windows or turn on a fan. When preparing to paint and painting, you'll want the room to be well ventilated. If you do not have proper ventilation, painting can make you feel sick.
Change into your painting clothes. Put on your gloves and safety goggles. Look over the walls that you are going to paint. Remove all nails, screws or other additions to the wall. Spackle any uneven spots. Once the spackle dries, sand it down until the wall is even.
When your spackling is complete, line anything around the walls that you do not want painted with tape. Be careful taping so you cover all of the necessary parts of walls, borders and the floor. As you prepare to paint a room, you want to make sure that you'll only be painting the parts of the room that you want painted.
Line your floor with newspaper. Tape the newspaper down, if possible. This way, if you drip primer or paint, it will only stain the newspaper, not your floor.
Get a wet rag ready. Mistakes happen when painting, so you'll want this rag on hand in order to remove any wet paint that gets in places that it should not be. It may be 100% effective at removing the paint, but it's better than letting the paint dry and trying to remove it later.
Prime your walls. Paint the primer on the walls as if it were regular paint. Make sure to line the edges of the wall, as well as painting the main parts of the walls. Cover all parts of the wall evenly. Make sure to cover all imperfections in the walls, because they may show through if they are not covered correctly.
Let your primer dry, then begin painting! Paint as many coats as necessary, and you'll have a beautiful, painted room to enjoy.