Add Project Folders to Places
Create shortcuts to your frequently used project folders using the Places list along the left side of the standard AutoCAD file selection dialog box.
To add a shortcut, navigate to the desired folder and pick Tools > Add Current Folder to Places. By default, the new shortcut has the same name as the current folder. If you use a standard project folder structure this name may be next to useless, so take a moment to rename it by right-clicking on the shortcut, selecting Properties, and changing the Item name to something meaningful, like the project number.
Clicking a shortcut on the Places list takes you straight to your project CAD files. Do not pass Go, do not collect $200.
Bonus Tip: The Places list also has a History shortcut that allows you to quickly open previous drawings. This list can get really large. Autodesk recommends that you periodically remove unwanted history shortcuts to improve your performance.