Before a reading can be done, I need to chose a spread or card layout. That is, deciding what each position represents and what the selected card symbolizes. Although the assigned meaning varies with the nature of the question, most spreads are based on common geometric shapes; circle, square and triangle. Only once the spread has been designed can the deck be shuffled, and cards pulled. Each email reading includes a diagram of the spread used, and meanings assigned. Two examples from Concise Readings are below.
As suggested in the Four Card Spread illustration above, it is also possible to assign multiple cards to each space. That might be two cards from the same deck, or (in a Complex reading) one from a standard 78 card tarot deck and a card from an oracle or other specialty deck. The author of the Sacred Path and Medicine Cards describes a spread using both decks in the Sacred Path Workbook.