Do I put the period inside or outside the quotation marks?
The period always goes inside the quotation marks. (This, however, is not true for other punctuation marks.)
The main problem that people have with using quotes is also a fundamental one: does the period at the end of the quote go inside or outside of the quotation marks?
The period is unique among punctuation marks in that, yes, it always goes inside the quotation marks. For instance, He said, “I’m going to the mall.”
However, this is not the case for all end punctuation marks. For other punctuation marks, where the closing punctuation goes depends on which idea it refers to (the sentence or the quote).
For example, if the sentence is a question, but the words in the quote are not, the question mark would go outside the quotation marks. For example, Has he already said, “I’m going to the mall”?
If, on the other hand, the sentence is not a question, but the words in the quote are, then the question mark would go inside the quotation marks. For example, He asked, “Can I go to the mall?”