When a paint job looks great, it's usually because of work you never saw. Prep is the difference between crisp lines that last and a room that looks tired again within a year.
It starts with protection: furniture moved and covered, floors covered, outlet and switch plates removed, and fixtures masked. Rushing this step is how paint ends up on hardwood floors.
Next come repairs. Nail holes, dents, settling cracks, and gaps between trim and wall get filled, sanded smooth, and caulked. Patched spots get primed so they don't show through as dull patches in the finish coat, a problem painters call flashing.
Then the paint: cutting in by hand along ceilings and trim, rolling walls in consistent sections, and usually two finish coats for even color. Sheen matters too. Flat or matte hides imperfections on ceilings and walls, while satin or semi-gloss holds up better on trim, doors, and bathrooms.
When you collect painting estimates, ask each contractor what their prep includes. The answer tells you more about the finished job than the price does.