University selection is one of the first steps for applying to US Universities. One can apply to four to eight Universities depending on your interest, time and resources available. Though academic excellence should be the main factor in the selection of Universities, other important factors to be considered are cost of attendance, location, job prospects, research work etc.
For MS and PhD programs, research is the core of education. Find out what type of research interests you and which Universities and Professors are doing research in those areas. Admissibility should be a factor in making the final selection. If you have an average profile and a not so great GRE score, it may make more sense to apply to medium ranked schools. Find out what is the profile of the applicants admitted to a particular University and evaluate your chances accordingly.
University Selection: Importance of research
MS and PhD programs in most cases are focused on research. These are research based degrees, but a significant amount of classroom study is also required. If you are applying for a research based degree, the type and quality of research in a particular University should be the most important criterion for University selection. Visit the department websites and follow the links to research. Also faculty websites have a lot of information on the type of research they do. For Ph.D. students, the future job prospects depend on their research work and quality of papers published. So it is important to join a University which offers research in your field of interest.
It is not required to decide what exact research topic you want to pursue in the beginning, but you should have some general idea. In the Statement of Purpose the focus should be on what are your research interests. It will also demonstrate that you took the trouble to find out the research areas offered by the department.