Make the basic shape of the card. This can be something as simple as folding a piece of paper in half or more complicated by choosing a shape. For a winter occasion, cutting out snowflakes and decorating them will make a personal card appropriate for the season. Also, choosing decorative papers or card stock can make simply folding the paper in half still appropriate for any holiday.
Write the greeting. Let the person receiving the card know exactly what you are thinking. It can be as simple or as complicated as you choose. The type of occasion that the card is for and how well the person is known will all determine what is written. For example, many just write "Happy Birthday" while others may prefer to write a more lengthy message. Traditionally, something basic is written on the front and a more personal message is written on the inside.
Decorate it. There is no one way to decorate a card and there are no limits. As long as the greeting is visible, you can use anything. Decoration starts when choosing the paper or card stock. Next, use any paint or heavier background material and allow it to dry before continuing. Afterward, add things such as ribbon, buttons or other small items. Glue heavier decorations onto the card using a glue gun in order to ensure that they stick.