This book gave me a great foundation in graphic design principles and gave me the language i needed to guide my learning? Design Basics Index: A Graphic Designer's Guide to Designing Effective Compositions, Selecting Dynamic Components & Developing Creative Concepts
A good starting point would be to familiarize yourself with the concepts in this book.
A lot of great tips in this thread too!
This series of books: http://www.amazon.com/Design-Basics-Index-Jim-Krause/dp/1581805012