A summary is a brief account of the main ideas of a work. 

The length of your summary depends upon the work you are summarizing and how many main ideas the piece has.  You want to keep a summary short and not just rewrite the piece but find the main ideas of the piece and then rewrite them being careful not to plagiarize.  A rule of thumb is that each paragraph can have a new main idea depending on if you are summarizing an article, essay, or textbook.  A piece of literature may have less and instead have main ideas suggested by the author’s themes and messages for the whole work.

To effectively summarize, I suggest you do the following:

1.   Read the article underlining or writing down the main ideas presented in it. If it’s non-fiction, follow the one idea per paragraph rule although it may not be structured exactly that way. 
2.   Take that outline and put the main ideas in your own words making sure you include some signal words or phrases like, “The article also states . . . “ or “Another main idea of the article is . . . “
3.   Make sure you include the title of the work and the author at the beginning of your summary. 
4.   Don’t present your own personal opinions since a summary is just a writing that outlines another work’s main ideas.
5.   Make sure you cite your source correctly if asked to include a bibliography.
6.   I tell my students that a summary should be one-fourth to one-third the length of the original work.  Keep your summary short and sweet, but remember to summarize the entire work. You can also combine ideas with the use of sentence variety.