Create a new letter size document in Illustrator, portrait orientation, RGB color. Show the rulers (cmd/ctrl + R). Right click the ruler and set the units of measurement to inches.
Drag guides to divide the page into quarters. To do so, drag a horizontal guide from the top ruler and drop it at 5.5" and then drag a vertical guide from the side ruler and drop it at 4.25". This will help you position elements of the card. The top of the page will be the front and back of one card, and the bottom of the page will be the front and back of the second card. In the layers palette, double click in the layer name and change it to "outside".


