Many writers overuse capital letters in body text.
There are also rules about capitalization within abbreviations, but I'll discuss those rules another time. The first rule is so obvious that some word processors automatically capitalize words that begin a sentence. And few people have trouble with proper names of specific people, places and organizations. However, beyond the obvious, many people are not sure what a proper noun really is, and even the experts sometimes disagree. The word 'company,' for example is obviously a simple noun.