There is some consensus to draw an odd number of cards, count positive versus negative cards to determine yes versus no.
The problem with this solution: there is no 100% consensus on the exact list of positive versus negative cards.
Andy Boroveshengra: neutral-negative Book, neutral Ring
Rana George: neutral Book, positive Ring
Another solution from the old-school cartomancy with playing cards: count red (heart, diamond) versus black (club, spade) to determine yes/no.
IMHO the latter solution works best for me, in this case I will avoid the discussion about positive/negative cards, but on the other hand there is some discussion about positive/negative suits, spades in Lenormand are much beneficial than in other old-school cartomancy systems.
I did yes/no with other systems for a while (coin toss, ifa, i ching, playing cards)…determining probability factor might be influenced by wish-fulfilling thoughts, so the most confronting question is: am I willing to accept an answer that goes contrary to my own beliefs? otherwise I am only looking for confirmation of my own wishes. but still the oracle might answer me with a problematic ‘ this is what you fear’ in a Yes/no answer. It is then so easy to refuse the problematic answer and try another system instead.