If your field names are complicated, a strategic use of capital and small letters in combination with underscores and numbers is the best way to create them. For example, if you are going to have 25 different donor interest fields, naming them Arts, Education, Public_Health, is fine. Or you could name them Interest_1, Interest_2, Interest_3, etc. The labels can be Arts, Education, Public Health, etc.
Although it is possible that some special characters can be used when creating FieldMaker fields, you should use only numbers, letters and underscores. Dashes and spaces are unacceptable. Other characters will cause problems in reporting, data grids, merging in Word and opening the data in Excel.