1) For documents cited in Oregon court filings I recommend starting with the free, official, and online OJD Appellate Court Style Manual.
You can link to that PDF, but I prefer going through the live OJD Publications website to make sure I have the most current version (the print/PDF Style Manual says 2002, but it has been updated since then).
2) You sometimes, though rarely, need the Bluebook (Harvard et al). The Oregon Appellate Court Style Manual will tell you when you need to go to Bluebook.
(For help with the Bluebook, try Cornell’s “Introduction to Basic Legal Citation,” by Peter W. Martin.)
3) Another style manual used in many legal research and writing classes, but not always by Oregon courts is the ALWD Citation Manual.
4) Sometimes a quick and dirty way to figure out how to diagram a tricky citation is to use a legal database (e.g. Fastcase, Westlaw, Lexis). Search for the document (or type of document) to see how the court(s) cited to it.
5) Last, but not least, with all the online unofficial cases and statutes floating about, it’s sometimes hard to know how to cite to “advance sheets,” “slip opinions,” etc. I have 2 Guidelines for citing those:
a) Check to see if there is a Bluebook or legal citation example or rule that applies to a document similar to the one you need to cite.
b) Put yourself in the shoes of the judge, librarian, or lawyer who is reading your letter, memo, brief, or article and ask yourself: “Would the reader be able easily to find an official or almost official copy of the case, statute, etc. with the information I have provided in the citation?”