How do you do that!
First step in scheduling is to break the project product into (measurable, verifiable and assignable) deliverables, which defines the scope of the project.
You can achieve this by creating a work breakdown structure (WBS). As per PMBOK®, a WBS should be deliverable oriented logical break down structure and also a WBS with only phases and activities without deliverables is NOT a WBS.
So, first identify the deliverables in your project. If your project is small, then it is easier to identify the deliverables. Otherwise, you can break the project into time-phased phases (first-level) - also called as stages - and then further break down the phases into deliverables.
Now, the next step is to identify the tasks to accomplish the deliverables. In top-down approach, you should identify the deliverables first and then determine all the tasks and only those tasks to accomplish the deliverables. In bottom-up approach, you should brainstorm to identify the tasks first and then group them under their deliverables.
Which approach is best?
Both are successful. If you are new to WBS, use the bottom-up approach otherwise use the top-down approach. If you have used top-down approach to create the WBS, then use bottom-up to validate the completeness.
A good WBS should satisfy the below rules
1. Your WBS should be have more than one level
2. There should not be any overlap between the phases, between the deliverables or between the activities
3. Each element in the hierarchy should relate and only relate to its higher level element
Remember, a WBS specifies explicitly what should be done and implicitly what should NOT be done.
PMBOK® - A Guide to the Project Management Body of Knowledge, published by PMI® .