Either way: part-owner or part owner seems acceptable (but the spell checker here at WikiAnswers does not like the hyphenated version!)
According to the sources I've found on a quick search, you should hyphenate 'coauthor', i.e., it would better be: "co-author".
You do not hyphenate the number.
responsible
??
You should hyphenate well nourished and well developed IF followed by a noun - i.e., "well-nourished and well-developed man" or "well-nourished and well-developed patient". If the noun is before these, then you would not hyphenate - i.e., "The patient is well nourished and well developed". This would also be true for the following: "well-healed scar" or "the scar is well healed". Answer provided by a medical transcriptionist with 18 years experience.
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 the sources I've found on a quick search, you should hyphenate 'coauthor', i.e., it would better be: "co-author".
You do not need to hyphenate.
You do not hyphenate the number.
You would hyphenate "thank you" when it is used as an adjective before a noun, such as in "a thank-you card."