[header] How to create clean paint edges on interior walls [title] Clear the room! [step] If that is not an option, move everything to the center of the room. Remove pictures and nails and anything that you do not want painted. [title] Use drywall spackle to fix bigger holes, or use painters putty to fill in nail holes. 
[step] Nail holes are obvious after you paint so take the extra time and make the room look good by filling the holes. [title] Wipe off the trim edges with a damp cloth to remove any dust so that the tape has a good surface to adhere to.