The Purdue OWL site has some helpful exercises to practice paraphrasing.
Paraphrasing is not simply rearranging the words of someone else's sentence. Nor is it replacing their words with synonyms. It is taking the gist of their idea and putting it into your own words. IT MUST BE FOLLOWED BY A CITATION. When should you paraphrase:
If you are looking at a large amount of material, a paragraph let's say, you do not want to paraphrase line by line. Instead, you want to focus on reading the whole section and take out one main point. Can you summarize that section into one main idea sentence?
If your paraphrase is too close to the original content then it is better off to use quotation marks and just use the direct quotation.
Original Text from "Irish Immigration." Immigration. Library of Congress, n.d. Web. 23 Jan. 2014:
"Their [the Irish's] organizational ability coupled with the large number of Irish living in U.S. cities, made the Irish a powerful political force. They literally transformed politics in American cities by putting local power in the hands of men of working class origin."
Bad Paraphrase:
The Irish changed politics in American cities. Men of working class origin were given local power and because of their organizational ability along with their large numbers living in U.S. cities they became a powerful political force.
Acceptable Paraphrase with CITATION:
The Irish wielded great political power, particularly in the cities. By empowering the working classes this ethnic group became a powerful and influental voice in politics ("Irish Immigration").