The first nine rules in the Bluebook apply to all of the other rules and they are all about style.
For example, if you are citing a secondary authority with a title, consult Rule 8 Capitalization, to know whether you need to capitalize certain words or not.
Another example: page numbers - how do you know how many digits to include in inclusive page numbers. Is it 113-119? Or, is it 113-19? Or, is it 113 to 119? Rule 3.2 helps you understand what to do with numbers.
Citations are to the 20th edition of The Bluebook, A Uniform System of Citation.
One mistake students and attorneys alike make is assuming that research systems like Westlaw and Lexis Advance provide properly Bluebooked citations. This is usually incorrect, but the citations these services produce look pretty good. Be sure to verify the components of a proper citation, especially the abbreviation. A citation copied directly from Westlaw, in particular, is easy to identify, because the source name will be an abbreviation, but not one approved by the Bluebook.