Picking your postgrad university is a major decision and not one you should ever take lightly. Chances are you are going to be spending a lot of money and time on your chosen institution, so making sure you pick the correct place for you is paramount. It's not just about picking the highest ranked university, the one with the best choice of courses, or the one which fits you geographically. Ideally, you want one that matches all of the above.
As with most countries that offer further education, centres of learning in the US are subject to rankings based on various aspects of their operation. These range from student satisfaction through to teaching standards and the combination of each of the scores should give you an idea if the university you're looking at is right for you. Obviously, as with all statistical reporting, the individual might have a different view of things, but rankings do offer a good overview in terms of judging quality. You shouldn't make hard and fast decisions based solely on ranking figures, but you can use them as a pretty good guideline as to what each institution has to offer you. University ranking figures are usually compiled by independent sources and are based on student input so they can be relied upon to provide an accurate picture.
Two of the most important factors to look at with regards to rankings figures are student satisfaction and graduate employment scores. While the whole package is important to look at, these two give you a good idea of whether you will enjoy the course and whether the course will benefit you in the long run. It's still very important to make sure the quality of teaching is good and the location of the university is right for you, but these two statistics should be top of your list.
There are dozens of places that offer university rankings but probably the most valuable resources are the Times Higher Education World Rankings and the QS World University Rankings. As British and American rankings, they tend to favour their home universities each year, but both give a really in-depth rundown of the strengths and weaknesses of US Universities. The QS rankings will give you an idea of what's important to US Post-grad students, while the Times rankings will give you an excellent idea of what to expect as a foreign student.
As mentioned above, rankings should only guide your decision, not form it completely. You should be looking at the universities website and course specific sites to see what the programs they offer entail, and whether they match your specialisations. You can consult the rankings during your search, but you should always be drawing your conclusions from the whole picture. One good way to use rankings is to pick out two or three establishments that you are interested in, based on rankings, then research them in depth afterwards. That way you know you're looking into known quantities. If you start out deciding to research establishments that score highly in the ranking, you won't be disappointed when you find out your chosen institution scores poorly in a category that matters a lot to you.
Whether you're just starting out on your search or you're close to making up your mind, US ranking figures can give you a real insight into the various choices you have in front of you. If you haven't begun looking yet, then focusing in on universities that score highly in things like student satisfaction or graduate employability could be a good place to begin. If you're interested in a particular establishment but aren't sure whether it's right for you, then consulting the rankings might confirm any suspicions you have or waylay them completely. Whatever you do, you need to be taking the whole picture into account. University rankings are a great start point and a great way of firming up a decision, but make sure you're doing the extra research and finding something that's just right.