Most students use too many quotes when they write. They quote textbooks and other routine information simply because it sounds better than they could come up with on their own. Quotes should be used sparingly and dramatically. It is seldom necessary to quote factual information. Use quotes from primary sources, for emphasis, or to give credit to someone's analysis.
Quotes also tend to be more dramatic and emphatic if they are short.
To reiterate an earlier point, never write about anything you're not prepared to discuss or explain verbally. The problem is that they often try to present complicated research from experts on the subjects about which the student is just learning. Delving into complicated sources can cause a student to plagiarize. You will find yourself using terms you can't define, case studies you don't understand, and expressing opinions that are not your own. You would be better served to discuss what you do know in greater detail than in trying to add things you don't comprehend.