- Denomination: Try putting together a complete set of all the different denominations issued by the United States. Start with the coins in circulation and then include obsolete coins like a half cent, a three-cent piece, a 20-cent piece — coins that most people have never heard of.
- Type: You'll find a number of different types within each denomination. For example, half dollars include the Flowing Hair, Draped Bust, Capped Bust, Seated Liberty, Barber, Walking Liberty, Franklin head, and Kennedy types. You can collect by type within a denomination, or you can expand into other denominations.
- Date: Collecting by date is a fun and affordable way to obtain every date for a particular series. For example, you could easily collect a half dollar from every year they were minted since 1900. There's no reason to pay extra for a rare mintmark — just pick the least expensive coin for the year and add it to your collection. Not only will you have one coin from every year, but you'll have added several different types along the way.
- Date and mintmark combination: Collecting every date and mintmark combination becomes a bit more challenging and expensive. Most series have a rare mintmark that can sometimes be prohibitively expensive. You don't want to attempt to collect a set of Barber dimes unless you have a lot of money. You may find and be able to afford every date in the series except for the extremely rare 1894-S — you'll need $1 million or more for a nice one! On the other hand, there are several series that you can complete without breaking the bank. If you can't afford the Barber dime set, try the Barber half dollars instead. The coins are bigger, and every date and mintmark in the set is affordable.
Keep in mind that until recently, coins minted in Philadelphia had no mintmark.
- Year: Many people try to buy every coin issued in the year of their birth. If you're under 50 years old, all you have to do is buy the mint sets and proof sets issued by the government in the year of your birth, plus any commemorative coins issued that year. If you're older than 50, you may have to search a little harder — but that's half the fun of collecting coins, isn't it? If you really want to go all out, try collecting coins issued in your birth year by other countries!