The default MText editor in AutoCAD (2002 and higher) offers a list of predefined symbols for quick entry in the edited text (right-click in the MText editor > Symbols).
You can add your own symbols and boiler-plate texts to this list. Run REGEDIT (Windows Registry editor) and add a new key "Symbols" to the MTEXT key in the HKCU portion for your AutoCAD version. Then add numbered pairs of "Name" and "Contents" string values with your data. The specified items will be automatically added to the MText Symbol list. You can even add these data while AutoCAD is running.
Try e.g. the following registry records - either add them manually or save this to a .REG file (attached) and double-click on it (please note your AutoCAD version/language code "8001:409" may differ; backslash is to be doubled only in the REG file):
Windows Registry Editor Version 5.00
"Contents 1"="CAD Studio a.s., Tylova 17, Ceske Budejovice, Czechia, www.cadstudio.cz"
This will add two new "symbols" - our Address and the Yin-Yang symbol.