While creating an entirely new chapter on capitalization would be fun, there are myriad resources online that are freely available.
Grammarbook.com, which also houses free quizzes to help students study, is an excellent source on capitalization rules: https://www.grammarbook.com/punctuation/capital.asp. I recommend using this page to answer most capitalization questions you may have.
There are some “rules” on capitalization that are disputed or followed irregularly, such as whether to capitalize a job title following a person’s name.
Example: “Please consult Montgomery Scott, Director of Engineering, for information about propulsion systems.” Most organizations capitalize in that case, but many official rule books suggest otherwise.
In matters of such discrepancy, consult your organization’s style guide if they have one. Many organizations have in-house rules for such points and will expect you to follow them. If your organization has no such style guide, consider using the Canadian Press Style Guide or a similar document to fill in. Or, at the very least, be consistent in your capitalization choices.
Oh, and one point to finish with, the word “I” is always capitalized. We all know that, right? Right?