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.
Notify stakeholders of project progress at regular intervals and gain their approval for any changes that substantially impact the deadline, budget or deliverables. Once the final product has been fully tested, staff have been trained (where necessary) and the stakeholders have signed-off the project then it can be implemented in the working environment.