In fiction, the first few words of a chapter are often either capitalized or formatted differently. Make these words consistent with the rest of the text. This may require changing the text to sentence case and re-capitalize anything that needs to be recapitalized (such as proper names). We do this because some screenreaders read UPPERCASE words as separate letters (e.g. U-P-P-E-R-C-A-S-E) which sounds like an abbreviation and is annoying.

Example of drop caps and capitalization that should be changed to sentence case: Drop caps and capitalization

Headings are an exception. All uppercase words in headings tend to be read as words, but if you want to change it, use capitalize each word or Title Case.

Change capitalization in Word