Reddit mentions of The Consumer's Guide to Effective Environmental Choices: Practical Advice from The Union of Concerned Scientists

See if your library has The Consumer's Guide to Effective Environmental Choices and read it. In a nutshell, the Union of Concerned Scientists research the impact of many kinds of spending choices and outline the biggest things you can change/the most important spending decisions you make in determining your impact on the environment.

>Paper or plastic? Bus or car? Old house or new? Cloth diapers or disposables? Some choices have a huge impact on the environment; others are of negligible importance. To those of us who care about our quality of life and what is happening to the earth, this is a vastly important issue. In these pages, the Union of Concerned Scientists help inform consumers about everyday decisions that significantly affect the environment. For example, a few major decisions--such as the choice of a house or vehicle--have such a disproportionately large affect on the environment that minor environmental infractions shrink by comparison.

Aside from that, be an informed and participatory voter!