Some CAD programs make it easy to insert special characters like ° or ±. I know Autocad has special key strokes for some commonly used special characters. With Revit you have to take a few extra steps to get special chacaters into Revit text (unless of course you want memorize many complex keycodes). The other advantage of this method is you have access to a pretty large variety of special characters like, ¼, ½, ¾. So you ask, how do I gain access to all these special characters! With Charcter Map, a handy little program that has been included with Windows since 3.1 These days in Win XP/2000 the best way to access Character Map is via the run command line. Go to your Start Menu, and click on "run". In the run dialog box type "charmap" and click "OK". This will bring up the character map program, a simple dialog box that displays all the charcters in the selected type style. You can then select and copy whatever characters you need, and paste them into your text in Revit (or any other program). Another quick hint, for very commonly used charcters you may want to make a list of the custom key strokes. The key stroke for a character is listed in the bottom right (if it has one), if it is listed as "alt+xxxx" then you will need to use your number pad to the right of the key board to enter the numeric code while holding the "alt" key.
Hope this helps, cheers,