The tasks need to be scheduled in the correct order and dependencies between tasks factored in. In complex projects several tasks will be performed in parallel to maximise the total project time. The plan will also take account of the project budget.
Regularly review estimates, deadlines and milestones to check they are still on schedule. If necessary, update the plan with new estimates and tasks and ensure that remaining tasks are necessary and estimates are still valid. Circumstances can change during a project but question every change and always refer back to the original business requirement as a corss-reference.