In all previous versions of Microsoft Project, from 1.0 through 2007, the question most asked of me has been, "How do I get Project to leave my schedule alone?" This question is convenience and usability based, not competency based. My answer has always been, "Let's talk about the goal and how the software can help achieve it." Naturally, discussion followed on how Project schedules and coaching or training solved the problem. Microsoft has addressed this common question brilliantly in Project 2010 with a new feature -- manual scheduling.
Manual scheduling allows the user to create and schedule tasks and resources without the interference of Project's scheduling engine. This means that Project won't be second-guessing the starting and ending dates when you enter a task or move a task to a different date. This is now the default scheduling setting in Project 2010.
There are several MPUG articles on the Manually Scheduled Tasks feature and its use in planning. (Read "Microsoft Project 2010 Feature Rally: Manually Scheduled Tasks" by Bonnie Biafore and "Microsoft Project 2010: Preparing for Launch" by William Raymond.) You'll also find a very nice explanation of Manual Scheduling in Project 2010's Help. Reading these is definitely worth the time.
Now my most frequent question is, "How can I have Auto Schedule (2007's default) as my default, but not lose the Manually Schedule feature when I need it?"
The answer is in Project's Options. Go to File, then Options. In the Schedule topic and Schedule section are the two settings that need to be set to meet your needs. If you want Automatic Scheduling as your default, just match the noted settings in the figure below and OK the dialog.

New projects will now be Auto Scheduled. If you want to manually schedule a task, you'll need to select the task and choose Manually Schedule from the Ribbon. See the figure below for its location in the Ribbon.

Regardless of your choice for Task Mode, Project will give you what you want. Now you can schedule your way.
MPUG memebers: Learn more about the manually scheduled task in an archived presentation made by Sam. Visit the Knowledge Library and view our WebnLearns-on-demand. Look for the recording published on August 4, 2010.
Sam Huffman, PMP, has been delivering training for The Versatile Company since 1996. Prior to joining Versatile, he was a member of the Microsoft Project development and support team. He has maintained his intimate knowledge of Microsoft Project with each new release and is considered a leading authority on the tool, including the newest enterprise features of all versions of Project and Project Server. During his tenure at Versatile, Sam has honed his instruction skills by delivering programs for thousands of people. His reputation for delivering practical wisdom with an upbeat style makes him one of Versatile's most requested instructors. Sam holds Microsoft's prestigious Most Valuable Professional designation. You can reach him professionally at sam.huffman@versatilecompany.com or personally at projectmanagementinfo@comcast.net.