When researching your family, it is important to record what source was used to gather the facts you have recorded. The way we record the specifics of a source is the citation, i.e. the author, title, publisher, web site url, date accessed, etc.
A lot of help is available for writing citations. First, if you are recording facts using a genealogy software program, good software will provide a template where you insert data, and the software will then generate a citation for the fact you have entered into your software program. Family Tree Magazine even has a handy "Source Documentation Cheat Sheet". You can download the pdf file here.
The Internet has links to a number of short, easy to follow guides for writing citations. I really like the simple, two page guide done by Thomas MacEntee on High-Definition Genealogy's web site. You might find it convenient to download the pdf file here then laminate it for referral as you work. Genealogical Publishing Company publishes similar laminated cards to help in writing citations. These show the basic components of information included in a citation and how citations for different types of sources are written.
Evidence Explained: Citing History Sources from Artifacts to Cyberspace by Elizabeth Shown Mills is considered to be the authority on genealogical citation. Perhaps your local library has a copy of this 800+ page book you can consult for assistance in writing citations. The book (also available as a purchased pdf download) covers not just print material but also the great variety of sources where we find information.
Confession time: When I first started recording information about my family, I wasn't as complete in citing the sources I used. I had a lot of simple citations like "1880 Census". Later when I needed to recheck data, I sometimes had problems locating my original source. Now I try to write better citations so it is easier for me or anyone else to locate and use the information I find.
Correctly written citations aren't so we get an "A" on our research. They are so we know specifically what information was used, where that information was located, and when it was accessed, all parts of documenting our family story.