PRINCE2 Principles
What the principles are
PRINCE2 rests on seven principles: continued business justification, learn from experience, defined roles and responsibilities, manage by stages, manage by exception, focus on products, and tailor to the project environment. They are the defining characteristics of a PRINCE2 project - a project that does not apply all seven is not being run according to PRINCE2. They are universal (they apply to every project regardless of scale, type or sector) and self-validating (they are proven in practice).
What you must understand
Know each principle by name and what behaviour it drives. Continued business justification means a valid Business Case must exist before the project starts and be maintained; if justification is lost, the project is stopped. Manage by exception means tolerances are set for time, cost, scope, quality, risk and benefit, and only exceptions are escalated. Focus on products means defining and agreeing outputs (and their quality criteria) before doing the work. Tailoring is itself a principle, not an optional extra.
Traps in questions
Examiners like to offer plausible activities that are not principles - for example "define a communication plan" or "hold regular team meetings". Another trap is confusing a principle with a theme (Business Case is a theme; continued business justification is the principle). Watch for options that describe applying only some principles, or that treat principles as optional depending on project size. Also note that principles are not techniques and do not prescribe documents.
Rule of thumb
If a statement describes why PRINCE2 projects succeed and applies to every project, it is a principle; if it describes what must be produced or addressed, it is a theme. Test each option: does it name one of the seven, and does it apply universally?
Worked example: "A project board cancels a project when forecasts show benefits no longer justify the cost." This demonstrates continued business justification - not change control, and not a process step.