“Anonymous” inquires: “How do you know what your ‘stop’ card is?”
A Stop card, as I have understood it, is a particular card that has its usual meanings if dealt any place other than the first card of a spread containing a minimum of 3 cards. If it is the first card in the spread, or the first card turned face up if the spread is dealt face down, then the reading is to be brought to an immediate halt and all fees refunded (if any). My card of choice is the 7 of Pentacles.
I did not have a Stop card until I started using the Thoth tarot. As I learned more about the artist, Lady Harris, of Crowley, of Thelema, and the esoteric paradigms that supported them all, I started to understand the astrological associations of the individual cards.
The 7 of Disks in the Thoth tarot is titled “Failure”, and has the astrological association of Saturn in Taurus, and the Kabbalah association of the sphere of Beauty in the elemental world of Earth. Nice mumblings there, but what does it mean? The sphere of Beauty (Netzach) is ruled by Venus. Venus is not exactly happy dealing with sticky, muddy, don’t-wanna-kiss-the-frog, dirt. So already there is discontent.
Then Saturn comes along, and plops his old and tired ass down next to her. His boots are filthy from trudging through the muck of Earth, and if that’s not bad enough there’s a damn herd of equally recalcitrant bulls in tow.
It is going to take a thirteenth labor of Hercules to get this house clean again.
Saturn starts shouting orders and expecting them to be fulfilled because he is older than dirt everyone. But no one comes in Venus’ house and tells her what to do. The movement of the bulls come to a halt and there is mud and stuff everywhere now.
Nothing is going to get done as long as these two stubborn and domineering characters are in the same room.
And that is my understanding why the 7 of Pentacles/Disks is called “Failure”.
After coming to that understanding, I noticed the first card of a spread usually sets the overall theme of the spread’s answer. It is not that great a reasoning then, that if “Failure” is the first card, then nothing good will come of that reading regardless of what positive cards follow. I started taking it as such when using the Thoth tarot. The habit spilled over when using my other tarot decks and the 7 of Pentacles has now become my personal Stop card, even though Waite (and Waite derived decks) have a much more positive interpretation of that card.
The habit has proven itself trustworthy over the years for me.
But that might not be the right card for you if you have other associations assigned to that card such as Waite does.
So now I come around to answer your question. If you want to use a Stop card in your readings, search your deck for the most halting card you can find. What one card, if used by itself, would mean “DENIED” in such a forceful tone, you can smell the red ink drying on the application. I would avoid using a Major Arcana card, as the so-called negative cards of the Majors are required for a healthy life.
Once you find a card that means such to you, if it shows up as the first card in a spread involving three or more cards, bring the reading to a halt. Of course, you could always proceed with the reading anyway and consider your Stop card to be a Warning sign instead. Take notes of the reading itself, and follow what occurs after. I had to be burnt by the aftermath a few times before I yielded and learned to trust my instinct about this card.