Writing summaries & common issues

Writing a summary sounds simple yet I find it very difficult.  Rephrasing someone else’s ideas in my own words seems to be my mental block.  What I seem to write are generalities about the article; it should tell the relevant details and main ideas.  A summary if not properly paraphrased could direct an audience a different way that the original author had intended and interject some of their own beliefs.  Worse off would be adding examples to the work.   A summary is not a critical review or an evaluation

While doing some research about summaries I came across this formula that gives me a place to start.  

In "Title of the Piece" (source and date of piece), author shows that: central idea of the piece.  The author supports the main idea by using _____________________ and showing that ______________________________________________________.

I found this at http://homepage.smc.edu/reading_lab/writing_a_summary.htm and found it to be a good starting off point if I have a mental block. A concluding sentence is the necessary missing element from this formula.