When you’re referencing documents manually, meaning that you’re typing the references yourself instead of having a software do it for you, then you’re following a set of rules.
Those rules might be imposed by someone else if you’re using an existing referencing style, like the Harvard Style (for a complete how to reference manually in Harvard Style, check this post!), the APA Style, the Chicago Style, the MLA Style, …
Or you might be doing it “free style” because your tutor told you that the style didn’t matter as long as it was clean and readable. “Clean and readable” means that you’re going to impose rules for yourself and follow them.
Whatever style or non-style you’re using, as you’re writing your reference list, you’re going to come up with questions. Should you add a period at the end of the reference? Which date should you write if you’re referencing a book chapter that was previously published elsewhere a decade ago? How do you distinguish two different authors with the same surname and initials?