Fill all holes and cracks in the baseboard with putty. Let the putty dry. Sand the dried putty lightly with sandpaper until its surface is smooth.
Place a strip of painter's tape along the edge of the carpet so that the tape's edge runs 1/4 inch up the side of the baseboard. Do this task for the entire room.
Tuck the edge of the painter's tape beneath the baseboard with a putty knife.
Attach tarps to the painter's tape you ran all the way around the room using painter's tape. Place the tarps throughout the room. This step is optional. If you choose to do this task, be careful not to tear the tape from beneath the baseboards when you walk on the tarp. If you choose not to do this task, be careful not to drip paint on the carpet. As an alternative to placing tarps throughout the room, keep your paint bucket sitting on a tarp or plastic bag to protect the carpet from drips in the immediate area where you paint.
Paint the baseboards slowly and carefully using an angle-sash paintbrush. The paintbrush should be about 1 inch wide or a different width with which you are comfortable.