Depends on what's being grounded, or in other words, how good the connection needs to be. Remember you're building an electric circuit. I'll suppose you're talking about "ground" as in the negative battery return. People are pretty good at seeing the positive side of the circuit: the battery post, clamp, heavy wire with lugs on both ends, fuse box, smaller wire going out to the load. The negative/return half of the circuit tends to be invisible. From the load you might have a short wire, a ring terminal, a sheet metal screw holding it to some body panel, a combination of sheet metal screws, bolts, and rivets holding a series of body panels together, somewhere a braid or heavy wire with lugs and bolts or screws connecting a body panel down to the frame, and finally a heavy wire with lugs and bolts connecting the frame back to the battery.
People forget all about those connections between the body components; they think of the chassis/body as a single unit. Electrically it isn't, though: anything that isn't welded together has a connection that may become loose, dirty, etc. When somebody is being really careful, perhaps because they're installing a radio transceiver or audio equipment, it's sometimes necessary to actually install jumpers between everything that isn't welded because though the mechanical connection is reliable, the electrical connection may not be. Common parts include door panels, the hood, fender panels that aren't welded, etc.
A shiny spot on the chair rail "could" be a good place for a ground.