Changing the Default Format to MS Office
Because most of the world is still using Microsoft Office, you might want to change the default format from OOo to MS Office.
Until Office 2010, Microsoft hasn't supported the Open Document Format (ODT), which is the default of OOo. Someone with a prior version of MS Office who hasn't heard of OOo will probably have no clue what to do with documents you send them. You can always hit Save As and select the MS Office format, but changing the default lets you simply hit Save.
Keep in mind, as OOo sometimes reminds you, that there are formatting differences between the Microsoft and OOo file types. This is another reason why you might want to change the default format, so when you create documents you don't have to convert them and risk it.
Although some special formatting and mail merges might not convert well between the formats, most of the common formatting (such as font settings, lists, and page layout) should work just fine.
When you're ready to change the default format click Tools > Options. On the Options dialog, expand the Load/Save settings and click General. Then choose the desired document types and select the MS Office format.