It has gotten a lot more competitive and difficult to get into a grad school now. Even for a non-ranked, low-tiered school, you will need a minimum of 1000 on your GRE.
The admission process for grad school is completely different from undergrad's. They usually careless about your GPA or GRE, and tend to focus on your research experiences, number of publications, internships, etc.
To my knowledge, admission committee will turn down applicants with 4.0 GPA and above average GRE if he/she does not have any research experience.