It is important that your organization thinks through why it needs to record time and what is required to do so. Some organizations see the Tasks page and think that this can be the way to record all time for the organization for both project and accounting purposes. The main focus of the timesheet in Project Server is to record actual work for project reporting. Your organization can use the Managed Time Periods, the Timesheet API, or perhaps other Project Server add-ins from Microsoft partner companies to integrate with accounting systems and to help create one-stop time entry. To do so takes a great deal of design, programming, and testing before you will be able to deploy a robust and accurate accounting timesheet function for your organization.
If project management is new to your organization, you might want to first consider using the timesheet for only recording project actual work and transition to an accounting timesheet after your organization has time to hone the timesheet update cycle process.
Take the time to train your project managers and team members to understand how entering actual work and remaining work affects estimates. The Work field increases if more time than what was actually estimated is entered in the Actual Work or Remaining Work fields. This is why it is so important to baseline your projects or project tasks before publishing your task data to the Tasks page. The Work field on the Tasks page is equal to Remaining Work plus Actual Work. To see the original estimate, you might want to add the Baseline Work field to that Tasks page.
Do not use the Manage Rules feature until your organization has some experience with using the Updates page manually. It helps the project managers to understand the process of task updates, the errors that can be made in time entry, and how the time is recorded in the schedule, before you create rules that automatically process this.