SNAPANG is definitely one way, but sometimes rotating the Z axis is a better method. With SNAPANG, only the Grid Snapping and ORTHO Mode rotates with it. So if you use Polar Tracking, SNAPANG doesn't do you any good. For non-symmetrical floor plans I usually rotate the UCS and re-align the PLAN to work in an "upright" drafting position. Here's an example:
This way, you manipulate the drawing space to work comfortably and freely. To get back to normal, simply type UCS and hit Enter twice (to reset the rotated UCS back to World), then type PLAN and hit Enter twice (to re-align the Plan View back to the UCS).
Current ucs name: *WORLD*
Specify origin of UCS or [Face/NAmed/OBject/Previous/View/World/X/Y/Z/ZAxis]
Specify rotation angle about Z axis <90>: 228
Enter an option [Current ucs/Ucs/World] <Current>: <ENTER>
Another tip: when rotating the UCS, you don't have to type in a direct angle, you can pick two points, or even simply select an object. I don't know if these options are available with your version as I am working on AutoCAD 2012.
Hope this helps some.