The model number is the difference between finding the right manual and finding nothing. Serial numbers tell you when the unit was manufactured — useful for warranty status and for ordering parts that changed mid-production. Both numbers live on a small metal or sticker plate called the rating plate, in a different place on every appliance type.
Top loaders: lift the lid and look at the underside of the lid or at the back rim of the tub opening. Front loaders: open the door and look at the door frame around the gasket — usually on the left side. Older units may have the plate on the back panel; pull the unit out to read it.
Open the door and look at the inside door frame, or at the front face of the cabinet behind the door. Some models have it on the back panel. Pedestal-mount stack dryers usually have it inside the upper door frame.
Inside the fresh-food compartment — usually on the side wall near the top, on the ceiling, or behind the crisper drawer. Some models have it on the kickplate at the bottom of the fridge. French-door and side-by-side models often have it on the side wall just inside the door.
Open the door fully — the rating plate is on the inside of the door panel near the top, on the side of the door, or on the door frame. Built-in dishwashers may have the plate on the kickplate at the floor.
Countertop: on the back of the unit or on the door frame inside the cavity. Over-the-range: open the door and look at the door frame, or at the cavity above the door (with the door open).
Pull out the warming drawer at the bottom and look at the underside of the cooktop or on the frame. Wall ovens: open the door and look on the door frame or on the side of the cabinet visible with the door open. Slide-in ranges: pull the unit out to read the back panel if you can't find it on the door frame.
Side panel of the outdoor condensing unit. Look for an aluminum data plate riveted to the housing. The model number tells you tonnage, SEER rating, and refrigerant type.
Inside the cabinet door, often on the inside of the upper panel. May also be on the top or side of the cabinet itself.
Once you have the model number, look it up under the matching brand page on this site to find the manual. If your exact model number isn't indexed, try the family number — the first six to eight characters of the model are usually shared across a model run, and the documentation transfers.