Cal State East Bay's academic policy lists plagiarism as a form of academic dishonesty. It tells us that plagiarism:

Includes taking the words, ideas, or substance of another and either copying or paraphrasing the work without giving credit to the source through appropriate use of footnotes, quotation marks, or reference citations.

However, there is no need to worry. Once you understand what plagiarism means in an academic environment, it is easy to avoid.

Source: Cal State East Bay - Academic Dishonesty

• Direct - The most obvious type of plagiarism. Copying portions or the entirety of another work into your own work, verbatim, without proper attribution. 
• Mosaic - This type of plagiarism is essentially bad paraphrasing. Including the ideas from another work in your own without proper attribution.
• Self Plagiarism - Reusing your own work without permission. Submitting portions or the entirety of work you have already submitted for a different course without permission from the instructor is a form of plagiarism.
• Accidental - Proper attribution is important regardless of intent. Presenting others' ideas as your own without citation is still plagiarism, even when it is accidental.

All types of plagiarism can be avoided by acknowledging the sources in your academic work with proper citations.

Purdue OWL

• Is It Plagiarism Yet?

Purdue University's Online Writing Lab (OWL) is the premiere online guide to citation. Here you will find the OWL guide to avoiding plagiarism.

Tests

Online quizzes to test your plagiarism knowledge 

• University of Southern Mississippi - A simple test on the basics
  
• Indiana University Citation/Plagiarism Test - A more advanced and challenging test
  

Video guide to avoiding plagiarism from Bainbridge State College