You can do a literature search for recent publications at a library, check out their websites, and talk to professors at your own school who might have some additional insights. This can be very intimidating and frustrating. Keep two things in mind. First, it is part of their job to talk with applicants. Second, remember that the GGE gets about 250 applications and that certain faculty, because of their interests, get the majority of the inquiries.
Emails are usually easier to answer.
Your goal is to concisely put your best foot forward. Ask them if they are taking students and would be willing to talk with you. If you don't hear back, send another email or letter. Briefly re-state your interests and refer to your earlier letter. Politely re-ask the professor if they are taking students next year and would be willing to talk with you.