This is my working reference of ideas for making decisions. Pair it with the Systems Thinking Cheat-Sheet: that one helps you see the situation, this one helps you decide within situations.

Three kinds of ideas

Kind	What it does	Examples
Model	Describes how something works	Maslow’s hierarchy of needs
Tool	A procedure you run	RICE, pre-mortem
Principle	A rule of thumb you keep in your head	Luck surface area, Chesterton’s fence

Deciding under uncertainty

Cynefin framework gives direction on how to approach a problem.

Decision-making model	What it says
Cynefin	Problems are clear, complicated, complex or chaotic, and each needs a different approach
One-way vs two-way doors	Decide reversible decisions fast and irreversible ones slowly
Pre-mortem	Imagine the project has failed, then explain why
Inversion	Ask what would guarantee failure, then avoid it
Expected value	Probability × payoff
Opportunity cost	The real cost of a choice is the best alternative you gave up
Satisficing	Pick the first option that’s good enough
OODA loop	Observe, Orient, Decide, Act; whoever cycles faster wins
Regret minimization	Which choice will you regret not making at 80?
Bayesian updating	Hold beliefs as probabilities and adjust them as evidence arrives

Prioritizing

Strategic work is important and rarely urgent, so it needs protecting.
Urgent work pushes itself onto your calendar; important-but-not-urgent work only happens if you book it.

Tool	How it works
RICE	(Reach × Impact × Confidence) ÷ Effort
ICE	Impact × Confidence × Ease
MoSCoW	Must, Should, Could, Won’t
Eisenhower matrix	Urgent vs important
Impact vs effort grid	A 2×2 of value against cost
Cost of delay	What does waiting cost per week?
Pareto principle	A small share of causes produces most of the effect

Thinking well

Strongest makers sit in “hidden craft”: the cheapest move is usually more telling, not more doing.

Principle	What is says
First principles	Break a problem down to what’s fundamentally true, rather than reasoning by analogy
The map is not the territory	Every model is a simplification
Chesterton’s fence	Don’t remove something until you know why it was put there
Occam’s razor	Prefer the simplest explanation that fits the facts
Hanlon’s razor	Don’t assume malice where confusion explains the behavior
Circle of competence	Know where your judgment is reliable and where it isn’t
Luck surface area	Luck = Doing × Telling: the more you make and the more people know about it, the more opportunities find you

How people behave

Model	What is says
Maslow’s hierarchy	Needs come in layers; higher ones only matter once lower ones are met
Jobs to Be Done	People “hire” products to make progress in a situation
Kano model	Features are basic (expected), performance (more is better) or delighters (unexpected); delighters decay into basics
Fogg Behavior Model	Behavior = Motivation × Ability × Prompt; if one is missing, nothing happens
Loss aversion	Losses hurt roughly twice as much as equal gains feel good
Peak–end rule	People remember an experience by its most intense moment and its ending
Diffusion of innovations / Crossing the Chasm	Adoption moves from innovators to the majority, with a gap between enthusiasts and pragmatists

How systems behave

The product mirrors how the teams talk.

Model	What is says
Feedback loops, stocks and flows	Systems are things that accumulate and change; reinforcing loops amplify, balancing loops stabilize
Leverage points	The strongest place to intervene is usually rules, goals or defaults, not more effort
Second-order thinking	Ask “and then what?”; the first effect is rarely the important one
Goodhart’s law	Once a number becomes a target, people optimize the number and it stops measuring what you cared about
Conway’s law	Systems mirror the communication structure of the organization that builds them
Tragedy of the commons	A shared resource is overused when each person gains and the cost is spread
Theory of constraints	A system moves only as fast as its bottleneck
Jevons paradox	Making something more efficient can increase total use
Network effects	A product becomes more valuable as more people use it

Strategy and position

Model	What is says
Innovator’s dilemma	Incumbents lose by serving their best customers well while cheaper, “worse” products grow underneath them
Wardley mapping	Map product parts by how evolved they are, from novel to commodity; build the novel, buy the commodity
7 Powers	Only seven durable advantages exist, including network effects, switching costs and counter-positioning
Porter’s five forces	Competitive pressure comes from rivals, buyers, suppliers, substitutes and new entrants
Optionality and the barbell	Keep most bets safe and a few small, wild ones with large upside; prefer choices that keep options open