You can initialize certain settings by selecting the Preferences item in the File Menu. These settings are saved in the "MuEdit Prefs" folder in the "Preferences" subfolder of the System Folder, and will be used in successive MuEdit launches until changed again. The settings that can be specified include:
Print margins (think Metric!)
How MuEdit should start: with a new window, standard Open dialog, or just nothing
Font and size for new documents. Note that old documents will be displayed with the style info (including fonts and sizes) with which they were saved.