The answer to this question depends on the type of paint job you're doing. If you're painting the entire room, then you'll want to start with the ceiling. This will help ensure that any drips or runs from the ceiling don't end up on your newly painted walls. If you're just painting one wall or accenting a specific area, then you can start with whichever surface you like. Just be sure to tape off any areas that should remain unpainted (like baseboards or trim) before you begin.