We usually use MLA format. There are other formats: MLA, APA, Chicago, Terabian, and more.
MLA stands for Modern Language Association. Their citations are easiest to learn. Once you learn theirs, learning another style is much easier.
Let's start with a book.
Find all information on the title page and the back of the title page (called the verso).
If you are in doubt about what the official title is or who the real author is, look on the verso for the Library of Congress Cataloging-in-Publication.
The CIP, as it's called, will show the title correctly. It will also show the author, but only the first one. Get the other authors from the front of the title page. NEVER get title information from the book cover.
Here is what you need for one book with one author. Write it in exact order with exact punctuation and capitalization as show in the following:
Last name of author, First name of author. Title. City of Publication: Publisher, Year of Publication.
Example:
Ballard, Charlotte. How to Be a Middle School Librarian. New York: Library Publishers, 2019.
This is the basic format for a book. You can add items to this format like subtitles, second or third authors, etc.
So think of that as the base of a citation. You always try to find the author(s), the title, the subtitle (if any), the publication information (place, publisher, and date).