Coin collectors often begin by saving coins they have received in circulation, but found interesting. These may be the remnants of change from an international trip, or an old coin found in circulation. Over time, if their interests increase, chance will not be sufficient to satisfy the demands for new specimens, and a potentially expensive hobby is born. Some become dedicated generalists, looking for a few examples of everything. If they have enough resources, this can result in an astounding collection, as that of King Farouk of Egypt, who collected everything (and not just coins either). Some are completists, wanting an example of everything within a certain set. For example, Louis Eliasberg was the only collector thus far to assemble a complete set of known coins of the United States.

At the very highest levels of coin collecting, it can become a highly competitive sport. Recently, this has exhibited itself in registry sets, where the most complete set of coins with the highest numerical grades assigned by grading services are published by the grading service. This can lead to astronomical prices as dedicated collectors strive for the very best examples of each date and mint mark combination.

Most collectors determine that they must focus their limited financial resources on a narrower interest. Some focus on coins of a certain nation or historic period, some collect coins from various nations, some settle on error coins or exonumia, such as currency, tokens or military challenge coins.

Every collector collects what interests them, and there are as many ways of collecting as there are collectors. However a few themes are common and are often combined to a goal for a collection.

A number of common collection themes include: