The set-up phase. Establishes the business case — a living document that justifies, at every gate, why the project is still worth doing — and selects an appropriate methodology (PRINCE2, PMBOK, Agile, hybrid).
Key facts
Business case = factual basis for go/no-go decisions; sized to project cost/benefit.
Should be reviewed and re-signed at key stages, not written once and forgotten.
There are many approaches and methodologies that are widely used across industry with organisations favoring standard industry ones (PRINCE2, PMBOK, Agile etc) or usually a modified version of these they make their own.
Setting up a project for success. A business case is the key.
The purpose of the Business Case is to establish mechanisms to judge whether the project is (and remains) desirable, viable and achievable as a means to support decision making in its initial and continued investment.
Provides a factual base for key decision makers to decide if the project should be undertaken.
Demonstrates how the project adds value to the organisation
Has a set of pre-defined standard organisatinal characteristics (costs, benefit, risk, etc.)
It is not all about size - size depends on the cost/benefit.
It is a living document throughout the project that should be reviewed and signed off at key stages.