Read your source material carefully. Go back over it once you're done to make sure that you've understood it completely.
Write down, in your own words, an explanation of what you've just read.
Compare what you've written to the source. Ask yourself if your paraphrased content conveys all the information in the original body of work.
Correct your wording, both to ensure that it reflects the meaning of the original and also to make sure it is not too similar to the original work.
Note the page number and bibliographic detail of the source if you're writing an academic paper. Even paraphrases have to be correctly attributed.