The question about reversals needs its own post, but I thought I'd answer a couple of the posted questions in the meantime....
I would like to hear your thoughts about using 2 or more decks in a reading.
Though it isn't a regular practice of mine, I have used different decks simultaneously while reading and it is a very interesting exercise. It's better left for those times when you have time to really reflect on the reading and not trying to shoot from the hip on some online pay-by-the-minute reading service. Some decks work really well together and others just will not speak to each other no matter how you ply them with bribes, so you kinda have to experiment with your decks to see which ones gel and which ones conflict.
Basically, it's kind of like doing a double card spread. You can do it two ways:
1. Lay out the spread in your normal way with one deck, then take the second deck and find all the cards that came up in the spread and lay them, in order, next to its mate of the first deck. Because deck imagery differs, each version of each card will shed a different light on the message.
2. Shuffle two different decks and lay one out in the spread, then randomly lay out the next "layer" of cards from the second deck. This spread would be read like a double spread, using pairs of cards for each position. This can be interesting because a card may show up twice in the spread in different positions because you are using two decks.
Another dual deck option is to use an oracle deck with your tarot deck. I have several and have found they can compliment a tarot spread very well, depending on your choices. I would recommend trying this method on a night when you have some time to really delve into the cards and soak up the imagery.
Katherine asked about "Quintessentials" of a spread: whether I use them at all, and what role they play in a reading. First of all, "Quintessence" is a classic alchemical term referring to aether. The aether was believed to be the substance which filled the region of the universe above the terrestrial sphere. Aristotle included it as a fifth element distinct from the other four, Air, Earth, Fire, and Water. Aether was also called Quintessence (from quinta essentia, "fifth element"). Quintessence was also supposed to be a definition of pure energy. Its force was imagined to be like a lightning bolt. In tarot, this term is used as a reference to a way of rather "distilling" all the cards, numerically, down to a number between 1-22 to get a "quintessence" card of the Major Arcana to sum up the reading or with which to relate the reading together.
One calculates the Quintessence card by adding up all the cards in the spread used, excepting the court cards, then reducing them down to a number between 1-22, with 22 representing the Fool. You can use this card to shed additional light on the reading and often it does relate rather well to the theme of the reading. It is not necessary to do, but it is a practice some readers use to add another kind of depth to a reading. I don't tend to use it, mainly because there has to be a very fine reason for me to do math.
Another practice some readers use is the "Shadow Card." This is the card at the bottom of the deck after the cards have all been shuffled, cut and laid out in the spread. Often readers don't even look at it until the reading is complete. It likewise tends to be used as a "summary" card or a card that gives additional information, advice, or warning. Once again, I tend not to use this card, and I'm not sure why I don't. It's just not a practice that became habit for me. Once again, try it and if you find you appreciate the information gleaned using this card, go ahead and incorporate it into your readings. Why not?
More answers to come. Meanwhile try these methods and exercises and let me know what you think of them.