Only if it is the first word in a sentence.
Yes, you should capitalize the letter after a comma in a sentence.
Yes, you should capitalize the first letter after a comma in a sentence.
Yes, you should capitalize "To Whom It May Concern" in a cover letter.
Yes you should.
No. it's not necessary.
Yes,it is a five letter word.
In "Sincerely yours," you should capitalize only the first letter of each word (Sincerely Yours).
You should capitalize the first letter of the sentence "Who is your favorite French artist?"
Yes, you should capitalize "Merry Christmas" and "Happy New Year" in a letter as they are greetings and proper nouns.
The pronoun "I" should always be capitalized.
Yes, you should capitalize the first letter of each word in "Thank You" when writing a thank you card as it is a proper noun.
Yes, if it used as the closing remarks.