You always want to begin a new sentence with capitalization
He never used capitalization when beginning a new sentence.
When using a proper noun, or begining a sentence
The word "its" is the possessive of the word "it," and "it's" is a contraction of "it is." The capitalization of the "I" simply depends on its location in a sentence.
Using capitalization on every word in a sentence is incorrect to do.Proper capitalization of certain words aids reading comprehension.Capitalization is not needed on every word of a book title.
Capitalization
You should use capitalization in writing for the first letter of a sentence, proper nouns (names of people, places, and things), titles, and the pronoun "I."
Not unless it qualifies for capitalization for some extrinsic reason such as being the first word of a sentence.
It depends on where you use it. If it is at the beginning of a sentence, then yes. If not, don't. (there are a few exceptions.)
The correct capitalization would be "Did your astronauts land on the moon?"
No, the word "motorcycles" does not need to be capitalized unless it is at the beginning of a sentence or part of a title.
The correct capitalization is:The closest star to the Earth after the Sun is the Alpha Centauri.Earth and Sun are specific bodies and formal nouns as used in this sentence. And the first word in the sentence is always capitalized.
You must remember your capitalization on your pronouns.Please check thoroughly for capitalization and punctuation.Market capitalization is how you measure the size of a company.