Some cases of unintentional plagiarism are due to poor note-taking from sources. For example, students sometimes copy down an author's exact words and forget to put quotation marks around them. Or they accidently mingle their own words with a source's words. Or they've forgotten to note the article title or author and can't find the source again when it's time to document the source in their research paper.
Here are some suggestions for avoiding these problems: