Card games are deceptively simple, but actually require a great deal of work to put together. Some card games use variations of the standard 52-card deck, while others use cards of their own unique design. The most elaborate card games are trading card games, which have thousands of different cards that players collect and build into specific decks. If you enjoy card games and want to design one of your own, it pays to follow a basic overall template.
Develop an idea for a card game. It can be as simple or elaborate as you like, but it must have certain specific traits to work. A card game requires a set number of win conditions to determine the victor. It also needs strategy options for players to adopt in order to reach those win conditions, but it must also allow for randomness, since the card deck will most likely be shuffled. In addition, you will need a hook to pique the players' interest: something simple and easy to grasp that provides the card game with a unified theme.
Determine the rules of play for your card game. This includes the turn sequence, the way players play their cards and the effect each card has on the game. The relative complexity of each turn sequence helps determine the pacing of the game, and particularly complicated card games may involve timing issues, which a clear turn sequence will help alleviate.
Draw up a list of all the cards in the game, outlining the rules of play for each one and the effects each one will have on the game. With some card games--especially collectible card games--the rules need to be fully described on the card's surface, so you should be as brief and succinct as possible.
Design preliminary versions of your cards using a graphic design program and print them out on your printer. They don't need to be fancy at this point; they just need to include all of the rules on their surface. Once they have been printed, cut out each one and slide it into a plastic card sleeve along with an existing card to provide backing. You can use standard 52-deck cards for this purpose, cards from games such as Magic: the Gathering, or even baseball or football cards.
Using the printed cards, play your game with friends to determine if there are any problems. Look specifically for "broken" elements that render the play too slow, too fast, too boring or too tilted in favor of one particular element. Keep play-testing until you are satisfied with the results, revising the rules of each card to match your play-test findings.
Create a formal graphic design for your cards. The front of each card should display the pertinent rules as well as a graphic element such as a picture that shows what it does. The back of each card should be uniform, which will prevent players from identifying individual cards during play. Graphic design programs such as InDesign or Photoshop are an excellent way to design a set of cards.
Write up a set of rules for your card game, formally describing how it should work. Your rules should include a breakdown of game play, a step-by-step example of a typical turn and a glossary defining any of the formal terms used in the game.
Print up final copies of your card game on card stock, or just use paper print-outs glued to existing cards from other games. If you have the resources, you can contact a print-on-demand service to print up professional copies of your cards. The service will provide specific instructions on the format it needs to print your card game.