These days, as the earth faces increasing environmental problems, we can expect more and more jobs to be created to help deal with these problems and to help promote conservation. Furthermore, a career in environmental conservation can be very fulfilling in the sense that it is for the greater good, and can give you the chance to work in some beautiful and remote locations in the US and abroad. Here are some ways in which you can prepare for an environmental career.
Join an environmental organization and volunteer with them in your spare time. This will give you good contacts in the field, and also help you learn about some of the career options in environmental conservation. Some of the big environmental organizations include The Nature Conservancy, The World Wildlife Fund, and The National Wildlife Federation. There are also many excellent smaller ones working at the community or regional level.
Major in a related field in college, or take some relevant classes. These can include ecology, wildlife biology and environmental science, and also classes in environmental economics, policy, social science, etc.
Do internships with environmental conservation organizations. This is perhaps the best way to get relevant experience and to get known by professionals in the field. It can take a while to get a permanent job in this field (such jobs being often in the non-profit sector, money can be tight and job openings relatively few) and the best way to get a foot in the door is to start as an intern in an organization you would be interested in working for.
Consider getting a graduate degree in the field. A master's in a relevant specialization will definitely help you get past entry level jobs in environmental conservation. An interdisciplinary master's program that combines environmental science with policy, economics and social science will make you a desirable recruit for many environmental organizations.
Join environmental job websites. Some are listed in the links below. Also attend networking events and happy hours where you can mingle with environmental professionals.