Project Managers typically know how to use a scheduling software tool such as Primavera or Microsoft Project, either from a training course, mentoring from colleagues or self-learning. However, despite this knowledge, many people utilize incorrect techniques in preparing their schedules. This paper is based on observations made by the author in reviewing project schedules for numerous clients over the years. Most of these schedules contained errors that greatly reduced the schedule accuracy and value. Based on these observations, this paper presents a list of the top 10 mistakes people make when preparing project schedules. Techniques that can be used to avoid these scheduling mistakes, along with a recommended schedule preparation procedure to help ensure that a schedule is accurate and complete, will also be discussed. This paper should interest people who are just learning how to schedule, as well as those who currently prepare schedules and want help in creating more effective schedules. If you think you are a skilled scheduler, read this paper to see whether you are making any of the common scheduling errors. You may be surprised! For more information on how PMCentersUSA can help your teams improve your practice in Project Management and Business Analysis, call us at 888-762-3683.