Troubleshooting a locomotive

I just inherited a locomotive that does not run. What are the first steps in diagnosing the problem?

A real live four foot eight and a half gauge locomotive? Where do you keep it so some of the experts can visit it. Or if it is a model, aren’t you better off on Classic Toy Trains or the Model Railroader?

WHAT TYPE AND GAUGE/HOW LONG IS IT BEEN SITTING?HEAR ANY SOUNDS IS THE POWER SUPPLY GOOD TRACK CLEAN?

HO guage, no sound.

check battery if any?

Model of a Diesel? Any idea of model? If steam, wheel arrangement?

Any indication of the manufacturer