Step 1: Explore careers via resources such as NEEF (National Environmental Education Foundation). Career OneStop: Careers and Career Information.
Step 2: Target your search by creating a list of likes and dislikes, keywords in environmental science, and ideas of careers to research. Create a list of potential organizations or companies you might like to work for e.g. US Govt EPA, The Nature Conservancy, World Wildlife Fund.
Step 3: Research the careers/jobs/companies/organizations and do some investigating.
Step 4: Talk to counsellors, career advisors, companies, teachers, and others that can help you understand the job(s) better.
A Guide to Green Careers