In the game of tarot, the fool possesses a unique role and has abilities that are unlike any other card as it is not considered to be part of the major or of the minor arcana. As far as using tarot cards for divinatory purposes, the fool has a clear cut message and meaning. The fool represents childishness. This can be seen in many different ways though, not necessarily all of them being negative. No matter where the fool card comes up, it can usually be seen in two or more very distinct lights. For example, if the fool card were to be drawn and placed in the romantic area of a spread, this could mean that the person who was being read was literally a fool for having chosen a certain path in a relationship. Perhaps they made a foolish mistake which put them in bad standing with a lover. Perhaps they fell for the wrong person. This could mean either of those things, or more.
A more positive way to look at the same thing would be if the person in question was a fool in love, that they would do anything, no matter how stupid, to win the heart of their true love. It could mean they are stupefied in their lover's presence. Taking the other meaning of the fool card, they could simply be childish about relationships, taking shortcuts, or cheating, not handling a relationship like an adult.
For another example, if the fool were placed on the spot on a spread that deals with finances, this could mean that the person has made a stupid financial mistake, perhaps investing in an unprofitable venture or wasting money on a scam. This could also signify a childlike irresponsibility with money, spending excessive amounts on toys when there are bills and things of a more important nature that must be attended to.
If the fool were to be placed on the spot in a spread which signifies career choices, this would most likely mean that the person in question has done something unintelligent in regards to their career. Perhaps they moved from one job to another which paid less, or perhaps they decided to move from one field into another less successful one. This is also a possibility. One more possibility that puts a more positive spin on things is if they are the type of person that treats their career with a childlike interest, in that they never become bored and are continually fascinated with it.
Finally, if the fool card is soon on a spread which represents health and happiness, this would signify that the person has made unintelligent decisions in regard to their health. A common one might be cheating on their diet, or taking up smoking or binge drinking. All of these things would be something that the fool relates to.