Well, no not really. you could hyphenate it but it would look silly and MS word would put those little red lines under it, which indicates an error. :) This is because the rule of hyphenation is used more commonly with numbers. For instance: Twenty-two vs Twenty two. The exception to this rule appears usually in surnames(last names) For instance: my last name is "Campbell-Gray". My mother chose this for me because she was not married to my father yet she wanted me to carry both her last name and his for life.
You don't.
Can you, or should you? You can hyphenate it if you're moving between lines in a paragraph and need to break up the word. You shouldn't hyphenate it normally.
McCarthy should not be hyphenated.
not required
A hyphen is not required.
Yes it should be hyphenated.
Yes it should be hyphenated: co-worker.
Yes it should be hyphenated.
Yes, hyphenate by-laws.
According to this style guide, yes it is hyphenated, though from standard rules it doesn't seem as if it should. http://www.gbps.org.uk/gbj_style.htm
According to the sources I've found on a quick search, you should hyphenate 'coauthor', i.e., it would better be: "co-author".
No, in general it is not correct to hyphenate certain prefixes, co-, pre-, mid-, de-, non-, anti-, etc. You therefore write preordain instead of pre-ordain, antidote instead of anti-dote, and midnight instead of mid-night.