Dress the part. Your audience will expect you as a tarot card reader, to look a certain way. Forgo the outdated gypsy bandannas and gold hoop earrings and instead opt for a smarter but no less striking outfit. Choose bright colors and accessorize with lots of charms, jewelry and make-up if appropriate. Make sure you are a very colorful and striking figure.
Have the props. Use a brightly colored scarf or other "mythical" garment to cover up the cards or use as an extra item when gesturing. Lay the cards out neatly on your table in some kind of pattern as you will not be convincing if the cards are clearly in a random mess.
Speak the language. There are hundreds of different types of tarot cards out there, all with varied names and descriptions so nobody will know if you invent your own. Use mythical and old fashioned names such as "Merlin" and "Llewellyn" that conjure up images of magic and sorcery. Attribute meaning to different figures such as "the priestess of darkness" or "the jester of deceit."
Be theatrical, the audience is there to be entertained so you mustn't disappoint. Close your eyes as if in meditation and make many arm movements when "summoning the power." Appear to be deep in concentration but punctuate the reading with gasps and wide eyes. Try to incorporate as many visible emotions as you can and use many gestures.
Have confidence. Like all actors or even con artists, self-assurance is the key to pulling off any stunt. Make your pronouncements in a strong voice and answer criticisms with a knowing smile or joking rebuttal. Behave as if you have all the answers and know something that the rest of the world doesn't.