How can you use the same iTunes across different users on your Mac?

I keep the iTunes folder & library in this path.

Macintosh HD/Documents/DigiMusic/iTunes

That way either my wife or I can use the same library easily when we switch users.

It's not a perfect solution. You have to remember to quit iTunes before you switch users or it won't open on the other side (file locked). There are also occasional issues where permissions must be reset.

We've done this for years. Now that we're in the cloud, it's not nearly so important so I may migrate away from this method someday.