A strong project gives you enough genuine material to explain what you personally did, why you made particular technical decisions, and how the work relates to your nominated occupation.
Start by listing projects where your responsibility is easy to demonstrate. Record the problem, your role, the technologies used, the decisions you owned, and the result. Projects with a clear timeline and accessible evidence are usually easier to describe accurately.
Avoid choosing a project only because it was large or prestigious. A smaller project can be more useful when you can explain your own contribution in detail and support the facts consistently across your resume, references, and project report.
Before writing, compare the project facts with the current ACS guidance and your nominated ANZSCO occupation. This is a readiness check, not a substitute for your own account of the work.