Below is an example of a project plan that I created for one of my projects.
I used Excel to create and manage this project plan. While there are other tools people use, such as Microsoft Projects and Confluence, I chose Excel because all project participants and stakeholders had access to Excel.
In the first column, you can a subset of the major milestones that were identified for this project. This was the starting point. I would recommend that you keep this high-level and attempt to break the plan into logical "big blocks".
From there, the project team helped define the discrete actions and owners associated with each milestone, gave estimates on how long each action would take, and the logical order for each action. I've found that team members may be hesitant to give estimates when they know you are going to use those estimates to establish commitments-especially when the work may be new to them, or they are new to the team. At times, I've had the "Agile" method used as a reason for avoiding dates. This is one of the reasons I recommend showing the entire project plan to the team. It is important that the development team understand that there are down-stream actions performed by other teams that also need lead time. Explaining that we need the dates to plan go-to-market activities in order to deliver the needed business results has worked for me.
Once I had this information, I used it to create a project timeline and schedule and to assign due dates to each action. I then vetted this end-to-end plan with the project team to get their buy-in and make any necessary adjustments. Our goal was to complete the entire project by September 19th, which is indicated by the green column.
When the project plan was created and socialized, I scheduled weekly cadence calls with the project participants to get updates on progress, understand issues they needed help resolving, and review the risk log. These weekly meetings allowed me to understand whether or not we were on track, and what issues the team was facing that they needed support in resolving.
I am happy to say that for this project, we were able to meet our September 19th deadline!
Attached is an Excel template that I use for project planning.