Fertility Friend has a free course that has all the info you will ever want or need to chart accurately to get that BFP! From the website:

This course will teach you the basic principles of the following:

How to understand your body's natural fertility signs and how to use them to achieve pregnancy.

How to confidently interpret and chart your fertility signs.

How to pinpoint your ovulation date by charting your fertility signs.

How to identify your most fertile days.

How to read fertility charts and recognize common fertility chart patterns.

How to maintain and take control of your reproductive health and communicate effectively with your health care providers.

Here’s the link: https://www.fertilityfriend.com/courses/course.php?cid=1