Here's how to avoid plagiarizing:
1. Know what plagiarizing is. Here's a good definition from Plagiarism.org.
2. Know what to cite. It's better to have too many citations than too few. Basically, cite everything (EVERYTHING) that isn't common knowledge. More about exactly what to cite here.
3. Don't write "blind," even if you are in a hurry. You won't remember where you got specific information later when it comes time to give credit and create citations.
4. Make sure your citations follow APA Style, so that your reader can find them. Your references list and in-text citations are like a road map the reader uses to check your credibility and discover new sources of information.