Check the school's accreditation status by calling a school official in the registrar's or admissions office. According to World Wide Learn, "In the United States, accreditation organizations are private and not affiliated with the government, though the government uses accreditation organizations to maintain the standards of the nation's colleges and universities." When asked, an institution is required by law to reveal its accreditation status and legitimate colleges and universities openly display their statuses willingly.
Research the history and reputation of the school. In addition to examining the literature provided by the institution in question, also use sources such as the Princeton Review and other independent assessors of higher education.
Contact professors, students, administrators and alumni of the university and ask them questions about the quality of the education, the hiring power provided by the degree and how the cost-per-credit compares to similar institutions.
Visit the campus or building that houses the school and ask to observe classes and other educational opportunities provided by the school.
Examine the degrees offered and the pricing options of the school. According to the Associated Press, degree mills tend to offer discounts if you agree to apply for multiple degrees or degree packages. Additionally, many degree mills tend to price per degree as opposed to per credit hour.