Clean the trim with trisodium phosphate (TSP) and a soft cloth or rag. The trim should be clean and without grease, dirt or dust.
Protect the room by placing drop cloths and painter's tape over floors, walls, and furniture. Painter's tape can also help to hold plastic drop cloths over doors or windows to protect the rest of your home from sanding dust.
Lightly sand the oak trim with foam sanding blocks. By using these blocks, you can sand into the grooves of the trim without harming the decorative ridges.
Vacuum the trim with the brush attachment on your vacuum. Use a tack cloth to remove any remaining sanding dust.
Use a paintbrush to spread the latex primer on the trim. The primer will help the paint adhere to the trim. Let the primer dry completely.
Paint the oak trim with latex paint and a paintbrush. Apply several thin coats on the trim, waiting the appropriate drying time before painting the next coat. Let the paint dry completely before touching.