To change default settings for a workbook, open Book.xlt, make changes, and then save the file. Don't change the file's name; you're just updating it. (It's a good idea to create a copy of the original Book.xlt so you can revert to Excel's original settings if necessary. Name the copy BookOriginalSettings.xlt or something similarly descriptive.) After changing Book.xlt, all new workbooks will use the custom settings you applied. To change a sheet's default settings, open Sheet.xlt, make the necessary changes, and save it.
If you don't have one or both files, simply create your own. Just be sure to save them in Excel's XLStart folder (\Program Files\Microsoft Office\XLStart).
