This ritual is taken from The New Orleans Voodoo Tarot.

In voodoo, activities or rituals that are said to "heat up" are used to bring power into objects or the participants. The purpose of this rite is to heat up or bring power into the cards so that the readings will carry more spirit, be more accurate, and be more easily understood.

First, rub your palms together, take up the deck, and let the heat radiate into the cards. This feeds a part of yourself into the deck, creating a link between you and the cards. Lift the deck and breath warm air between the cards. This warming creates a stronger link between you and the deck. Hold the deck before you and whisper that it is time for the spirits of the deck to attend. Chant the following verse to Papa Legba:

Odu Legba, Papa LEgba

Open the door

Your children Await.

Papa Legba, open the door.

Your children await.

Then, inscribe a crossroads in the air, and pass the deck through it. The deck moves into the land of the spirits as it traverses the crossroads.

Take one card from the deck and rub it between your hands. Let it absorb the oils your hand produces. Replace it into the deck without looking at it. Tell it to share what it has received with the other cards.

This will ensure the attention of the loas during your reading.