Instructions
Purchase a comprehensive shell identification guide if you have many shells that you're interested in learning about. Shell collecting is a popular hobby, so there are many books on the topic. Some are even devoted solely to specific types of shells, such as those that come from a certain part of the world (see Resources below).
Lay the shells on a table with enough room to move them around into clusters.
Separate them into groups according to which of the two main types of shells they fall into: gastropod or bivalve. Gastropod shells have one opening or valve, such as the kind of shell a hermit crab or snail would live in. Bivalve shells have separate pieces joined by a hinge, like clam or mussel shell.
Organize shells according to color, size, type or--if you have shells from different places--the area where they were found.
Consult your identification guidebook or a website (see Resources below) to help you figure out what kind of shell you have.
Having groups of shells with similar characteristics will make identification easier.