At minimum, before you hire any architect, make sure he or she is licensed. In the United States, the National Council of Architectural Registration Boards (NCARB) provides licensing, and each state maintains its own requirements and directories for licensed professionals. Just as doctors and lawyers must pass extensive testing before becoming full-fledged professionals, architects must pass the Architecture Registration Exam (ARE) through NCARB for licensing. So check with your state licensing board to ensure any architect you're interested in is properly licensed.
Finding a licensed architect who is environmentally responsible will involve additional research. You can start with the American Institute of Architects (AIA) Architect Finder for a listing of architects in your area, or do a simple Internet search. Having a broad sample to start with isn't a bad idea, and because most architects and design professionals have a Web presence with a CV and some representative projects, eliminating commercial architects or those whose style is widely different from your own should be easy.
Once you find a few licensed architects who specialize in eco-friendly designs you like, contact the firms and express your interest in their work. Ask about energy saving features and environmentally responsible materials and techniques from previous projects and insist on the hard numbers to back them up. Hearing data from the product catalogs or textbooks and codes is one thing, but building performance determines how effective features are. And in architecture, code books and specifications are measurable and precisely determined. If an architect skirts the numbers or won't present solid numbers, you might question how environmentally effective his or her projects are -- no matter how good they look. Remember, even though you're doing the hiring, the project should still be a collaboration between you and your architect, so being able to work together is important.
Next ask for references -- and check them. Clients who are pleased with their results are generally more than willing to provide a reference and details on their finished home, the process itself and anything that needed improving. Ask about specific environmental features that are -- or are not -- working out.
Of course, looks are important, so how do you find an architect to design a home you can live with for years to come? Start by creating a portfolio of your own.