When applying to graduate school, it is always advisable to contact the person(s) you might be interested in first to gauge their interest and seeing if they are planning on taking any students into their lab.
I like to receive a quick email from potential students that introduces themselves and briefly highlights what they have done and tells me what kind of research they are interested in. It is always a good idea to send a copy of your resume (cv) along as well that includes your GPA and GRE scores as well as your education, experience, etc. Why list the GPA and GRE? because we often have to gauge how competitive your application will be within our pool of perspective graduate students. That said, standards at the various schools differ.
Based on your interests, you should try to identify 3 or more faculty that interest you and then contact them all. Surely some of them will be taking on new students.