There is a video clip from Rutger's Robeson Library that introduces plagiarism in a funny way: http://library.camden.rutgers.edu/EducationalModule/Plagiarism/. I show the clip to my 6th graders (be sure to cut off the clip right before the end---you'll see why) as an introduction to the concept of plagiarism.
We then discuss plagiarism and the consequences of it. They often think they will go to jail. I say it is more likely they will get a poor grade and have to start a project over from the beginning. We do focus on the need to protect yourself on the web---many have websites, blogs, Facebook, etc. and put themselves at risk for greater consequences.
Next, the students look at a quick Powerpoint telling how to avoid plagiarism. Step 1. Take brief, bulleted notes, zeroing in on important facts. 2. Write original sentences based on these notes. 3. Credit your sources. The Power Point also discusses patchwriting, which is the kind of plagiarism my students tend to do. I model patchwriting for the students.
We then look at excerpts from World Book Online with two student samples beneath. They love to make up names for the students (Bertha and Frank). We read both examples and students work as table groups to decide who has paraphrased and who has plagiarized.
Next, students work in pairs to practice note taking and paraphrasing with support. We share ideas as a class.
Lastly, the students are assessed. They take notes on an article and then they write their own original sentences.
I'd be happy to share the documents that pair with this lesson. It is one of those lightbulb lessons, where I feel like my students really start to get it. Feel free to email me at email@example.com, if you'd like any attachments.