Plagiarism

Before reading the handout I was convinced that I had never committed plagiarism. However, now that I read the handout, I'm afraid that I may have plagiarised. I think I was at fault when I was paraphrasing other peoples work. In several papers I have written I read other peoples work online to give me an idea on the topic. I paraphrased it and didn't cite it since I didn't think I needed too. I am also worried that it was plagiarism when I have rewritten sentences or messages that I found on the Internet. I have often used the same idea and just reworded it in my essays, but I now know that its plagiarism. While I can continue to do this, I need to cite other peoples work in order to not plagiarize.