• Never base a judgement or decision on a single case, no matter how striking. In forming an impression of a person (or object) try to break your judgement down into his (or its) separate qualities without letting any strikingly good or bad qualities influence your opinion about the remainder.
• When exposed to connected material, suspend judgement until the end: try to give as much weight to the last item as the first.

• Think before obeying.
• Ask whether the command is justified.

• Think carefully before announcing a decision publicly: you will find it harder to change.
• When you embark on a course of action from which you do not want to relapse, announce it to as many people as you can.
• Ask yourself whether you are doing something merely because others do and if so, ask whether it really furthers your own ends.
• Don’t be impressed by advice from someone you admire he/she is an expert on the topic in question – and if he/she is remember that experts are often wrong.
• Don’t be stampeded by the behavior of a crowd into acts you would not commit in calmer moments. 
• Don’t fail to go to someone’s assistance because there are others present who might – or might not.

• Whether you are a member of a committee or a golf club, be careful not to be carried away by the prevailing views. Consider and express counterarguments.
• If you are informing a committee ensure that different viewpoints are represented.
• Be wary of forming stereotypes, but if you do, remember that not everyone will neatly conform to them.

• Beware of overrating the results of a choice you have made, particularly if it has cost you a great deal of time, effort or money.
• Try not to move by small steps to an attitude or action of which you would initially have disapproved.
• No matter how much time, effort or money you have invested in a project, cut your losses if investing more will not be beneficial.
• Value any activity or possession at the price it is worth to you now, regardless of the past.
• If you are persuaded to do something distasteful, try not to minimise its unpleasantness in order to justify yourself.

• If you want someone to value a task and perform well, do not offer material rewards.
• If you are a manager, adopt as participatory and egalitarian a style as possible.
• If you want to stop children (or adults) from doing something, try to persuade (explain your reasoning) rather than threatening them with punishment.
• Give people as much freedom of choice as possible, particularly in medicine and education.

• Search for evidence against your own beliefs.
• Try to entertain hypotheses that are antagonistic to one another.
• Be particularly careful to take into account anything that conflicts with your beliefs.
• Remember nobody is always right, though some people are always wrong.

• Don’t distort new evidence: consider carefully whether it could be interpreted as disconfirming your beliefs rather than supporting them.
• Be wary of your memory: you are likely to recall whatever fits with your current views.
• Remember that changing your mind in the light of new evidence is a sign of strength not weakness.
• Beware of being influenced by any explanations you may have concocted in support of your own beliefs.

• If you want to determine whether one event is associated with another, never attempt to keep the co-occurrence of the events in your head. Maintain a written tally of the four possibilities:

Event A and Event B
Event A but not Event B
Event B but not Event A
Neither Event A nor Event B

• Remember that A is only associated with B if B occurs a higher percentage of the time in the presence of A than in its absence.
• Pay particular attention to negative cases.
• Be careful not to associate things together because of your expectations or because they are unusual.

• Suspect any explanation of an event in which the cause and the effect are similar to one another, even when it is made on the highest authority.
• Suspect all epidemiological findings unless they are supported by more reliable evidence.
• Consider whether an event could have causes other than the one you first think of. In allocating cause and effect, consider the possibility that they may work in the opposite direction to that which you first plump.
• Be sceptical of any causal relationship unless there is an underlying theory that explains it.
• Remember that in most circumstances it is as reasonable to reason from effect to cause as from cause to effect.

• In apportioning responsibility for an action, do not be influenced by the magnitude of its effect.
• Don’t hold someone responsible for an action without first considering what others would have done in the same situation.
• Don’t assume that others are like yourself.

• Do not judge solely by appearances. If something looks more like an X than a Y, it may nevertheless be more likely to be Y if there are many more Ys than Xs.
• Remember that a statement containing two or more pieces of information is always less likely to be true than one containing only one piece of information.
• Guard against believing a statement is true because you know part of it is true.
• Remember that if you learn the probability of X given Y (for example, the probability that a cab is green if a witness claims it is), to arrive at the true probability of X you must take into account the base rate (the frequency of cabs).
• Remember that the frequency with which a given attribute or event is observed is likely to deviate more from its frequency in the population as a whole in small samples than in large ones. Don’t trust small samples.
• Beware of biased samples.

• Always work out the expected value of a gamble before accepting it.
• Before accepting any form of gamble decide what you want from it – high expected value, the remote possibility of winning a large sum with a small outlay, a probable but small gain, or just the excitement of gambling usually earned at a cost.
• Remember that whether you save £5 on the cost of a house or on the cost of a radio, the saving is equally valuable to you.

• If you are making a numerical estimate and have a given starting value, remember that the correct estimate is likely to be further away from the starting value than you may at first think.
• Remember that many small independent probabilities may add up to quite a large probability.
• Equally, if an event is determined by the occurrence of all of several other events, the probability of the event occurring will be very much lower than that of any one of the other events.

• Remember that when anything extreme happens, whether it is very good or very bad, the next happening of the same kind is likely to be much less extreme for purely statistical reasons: it reverts to the mean.
• When drawing predictions from imperfect evidence, make your prediction closer to the average value of whatever you are predicting than the value of the predictor.
• If two pieces of evidence always agree, you need only take account of one in making a prediction.

• Suspect anyone who claims to have good intuition.
• If you are in a profession, don’t hesitate to take decisions by using a mathematical model if it has been shown to be better than human judgement.
• When the importance of a decision merits the expenditure of time, use Utility Theory or a watered-down version of it.
• Before taking an important decision decide what your overall aim is, whether it be to maximise the attainment of your goals, to save yourself from loss, to make at least some improvement in your position and so on.
• Don’t value everything in terms of money unless you’re an accountant.