A citation...
describes a book, journal article, website, or other item
gives credit to the originator of an idea
enables the reader to access the cited item.
You must cite a source that you are using if you paraphrase or summarize any of the ideas given in the work AND if you use a direct quote from the resource (word-for-word). Citations are not just for word-for-word quotations; they must be used when you mention any ideas or information from a source.
The Excelsior Online Writing Lab, hosted by Excelsior College, can help you with each step of your writing assignments. Below is the website's navigation tab listing every aspect covered.
To avoid plagiarizing:
Paraphrase: put the ideas from the text COMPLETELY into your own words. Even when paraphrasing you must still use in-text citations as well as including it in the works cited section.
Use quotation marks around text that has been taken directly from the original source.
Cite every source of information you use in your paper unless it is common knowledge (i.e. the sky is blue) or the results of your own research.
MLA Handbook for Writers of Research Papers by Every discipline has their own citation style, however, every person/professor is different and they may have a preference for a different citation style, or prefer that you use an older format for citations. The books below are examples of the texts that can assist you with properly citing your sources.
Publication Manual of the American Psychological Association by 
The Chicago Manual of Style by 
The Concise Dictionary of Art Terms by 
Thames and Hudson Dictionary of Art Terms by The Purdue Owl Online Writing Lab has extensive information to assist with writing papers.
