When a resource is overallocated, use Microsoft Project 2010 to ensure your project stays on track. With Microsoft Project 2010, you can resolve resource conflicts by modifying assignments, changing scheduling, and more. Consider the following tactics to resolve resource conflicts:
Revise the resource's availability to the project. For example, change the person's availability from 50 percent to 100 percent.
Modify assignments to take the resource off some tasks during the timeframe of the conflict. The new Team Planner view is great for this purpose.
Move a task to which the resource is assigned to a later date using the Move Task tool or modify the task's dependency relationships.
Add a second resource to a task for which the overallocated resource is busy. Change the task to auto scheduling and effort-driven, if needed, to allow the task to be completed sooner and free up the resource earlier.
Replace the resource with another on some tasks. Try the Resource Substitution Wizard for help with this if you're using Project Server.
Select a task and then click the Inspect button in the Tasks group of the Task tab. The factors driving the timing of the selected task are provided so you can take whatever steps are needed to address them: for example if a task dependency is driving timing and you can modify that dependency, it might solve your problem.
Make changes to the resource base calendar to allow the resource to work more time in a week.