Before tracking actual work in a project plan, you should set a baseline. This provides you with a “snapshot” of your initial project plan for later comparison against actual progress and is one way to tell whether your project is on track.
The ability to track actual work in a project plan is a major advantage that a real project management tool, such as Project, has over a list-keeping tool, such as Excel. In Project, you can track actual work at a very broad or very granular level.
To properly evaluate a project’s status after you begin tracking requires a combination of recording accurate data in Project and using your good judgment when interpreting the results.