Sometimes we buy from other dealers. We exchange meteorite material with many of the world's major museums and educational institutions. We also receive dozens of rock samples a week from persons who believe they have found a meteorite. Iron specimens often contain indentations that look like thumbprints. Many meteorites have been uncovered by farmers while plowing.
Some discoverers just notice a strange rock and are persistent in their identification attempts.
Meteorites can be found anywhere by anyone. Anybody going searching would do well to arm himself with a powerful magnet, a metal detector, and some luck.