The following characteristics are common to most meteorites. Most meteorites contain some iron and tend to be very heavy.
Meteorites usually have a smooth surface with rounded corners.
Fresh meteorites will have a dark gray or black surface. Weathered meteorites will appear brown or rusty. At least some trace of fusion crust is usually visible on the surface. They really do look like they were made by someone pushing their thumbs into soft clay. The interior colors will differ, but after grinding or polishing, most will reveal tiny silver-metallic flecks.