Pet Peeve: In and Out -- (",.").

In and out: Quotation Marks, Parentheses, and the Placement of Periods and Commas

The rule is pretty basic but hard to remember. Periods and commas generally go inside quotation marks (in U.S. English). Periods and commas always go outside parentheses because the parenthetical is still within the sentence. If an entire sentence is within parentheses, the period goes inside.

Citing sources within a text: when you cite the source directly after a quote, the parentheses go outside the quotation marks and the period goes after the parenthetical citation because it is not part of the quote but is part of the thought/sentence.