Summarizing is a lot like paraphrasing, but of a longer piece.

Step 1: Understand the reading. Just like in a paraphrase, you can only summarize something correctly if you understand it.

Step 2: Identify the major ideas. What is the author trying to get the reader to do or believe? Look for headings, topic sentences, etc. to help you decide this.

Step 3: Identify the major supporting details. After you have step 2, try for one or two details that clearly demonstrate why the reader should do or believe what the author says.

Step 4: Turn these ideas into an essay. Make sure you change the vocabulary and the grammar of the original, or you are plagiarizing.

The summary should be about 1/3 the length of the original. In other words, a three-page article will turn into a one-page summary. This is a rule of thumb, not a rule.

The summary must include the author's name and the title of the piece somewhere within the summary, not just at the top or the end of the page. The full bibliographic citation, including year, place of publication, and publisher should be at the top or bottom of the page.

(from Deborah Healey - thanks Deborah)