Include the core information in a specific order. If you don't have that information for a source, you skip it. At its most basic, a citation should have Title, Publisher, and Publication Date. BUT ... this doesn't mean that's all you should include. If your source has it and it's on the list below, it goes in your citation!
What does this order look like?
Author. Always first, in the LASTNAME, FIRSTNAME format. If there's no author, start with the title of the source.
Title of source. Quotations around shorter works (like article titles and individual website pages) and italics for longer ones like books or complete websites.
Title of container. What’s a container, you ask? Wherever you found the source is the source’s container: The New York Times, Wikipedia, CNBC. A print book doesn't use this, but an ebook might!
Other contributors. Is there an editor? A translator? Credit them now.
Version. Is this a specific edition of the source? Put that here.
Number. Does the source have a volume and issue number? These should always be included!
Publisher. Who is responsible for this source getting to you? (Sometimes the publisher is the same as the Title of Container ... but NOT always!)
Publication date. When was this source made available to you? This is VERY important!
Location. Where was the book published (if relevant)?