Educate yourself about the various forms of financial assistance available from graduate programs. In general, programs offer fellowships and assistantships that carry teaching or research responsibilities. Many programs invite their top candidates for a visit. If at all possible, take advantage of such an offer. You can also volunteer to visit.
Visits normally entail discussions with faculty and students, receptions and tours.
Be pleasant and have a good time, but don't be shy. Instead, be inquisitive. Remember, it is YOUR future, so take the time to ask pertinent questions and secure as much information as possible to allow an informed decision should you be accepted to more than one program. Find out about the research programs of faculty, requirements of graduate students once in residence, and assistantships. Try to get together with graduate students for their perspectives on the program and faculty.