The American Psychological Association (APA) has established a style that it uses in all of the books and journals that it publishes. Many others working in the social and behavioral sciences have adopted this style as their standard as well.
APA's style rules and guidelines are set out in their publication manual:
Citation styles change over time. Be sure to only use the most recent resources that reflect the current edition. The current edition for APA is the 7th.
Below is a reminder of some common formatting details that sometimes are overlooked.