Personally I generally try to avoid using reversed cards if at all possible. Before each reading I make sure that the cards are all upright, if a card appears reversed during the course of my reading as sometimes they inevitably it will I may interpret it as an energy blockage but I usually disregard it. This as with anything concerning the Tarot is a matter of personal preference. Just remember that reversed cards are not simply the opposite meaning of its upright interpretation as some references seem to indicate.
It is better compared to the retrograde motion of a Planet in Astrology, the influences of this Planet (card) are often turned inwards thus the outward expression tends to be somewhat awkward. A reversed card is not fully expressing itself to its greatest potential.
A method that you can employ to interpret reversed cards is to lay another card over the reversed card to reveal how the energy can be allowed to flow freely. This will determine what characteristics need to be developed to overcome the blockage or perhaps the blockage itself. If the reversed card is The Tower for instance it could indicate that you are suffering from a powerfully internal transformation. Your inner foundations are crumbling and your values are being challenged slain and overcome. This is in contrast to its upright position where it could indicate external transformation. You could then do another reading to see how this inner conflict could best be resolved and what qualities are required to overcome the adversity.
Remember that reversed cards often represent that we are unable to deal with the energies of the card and thus it is manifests internally. Spiritual readers may also see this to be representative of karmic challenges resulting from previous reincarnations. Reversed cards can also be viewed as a stalemate point of soul growth that must be worked through in order to evolve to your next challenges.
Books You Might Enjoy:
Steve Roberts - Zhine Tibetan Dream Yoga
Aleister Crowley - Thoth Tarot Deck
Swetha Lodha - Your Love Life And The Tarot Cards
