You will have two major opportunities to make choices, deciding to which programs to apply, and deciding which admissions offer to take.  You will have many, many considerations to determine your choices, e.g., research interests, funding, career plans, housing, family, and other personal.  Choosing a graduate school will undoubtedly be a confusing task, and different people will give vastly different advice.  Lack of information will likely not be your problem.  Rather, synthesizing, prioritizing and ranking the information will be your challenge.

Today it is easier than ever to research graduate programs.  Every program has a website with full descriptions of the graduate program, faculty research, and admissions procedures. There are blogs, forums on the graduate admissions process, even specifically on physics.  Besides program websites you can use research indexes like Google Scholar to find out who is publishing papers in the research fields that interest you.

Every few years the National Academy of Sciences (NAS) releases an assessment and ranking of graduate programs.  US News & World Report publishes an annual ranking of graduate programs, and the website PhDs.org has a useful ranking tool that produces a list of best programs according to your own criteria.

Your professors are a great source of information and insight into different graduate programs.  This is one of the topics you should discuss with the professors you ask for letters of recommendation.  Your peers and current graduate students that you know are also great sources of information.

Attending conferences and recruiting fairs are also a great source of information.  There you will be able to make personal contact with faculty and students at a prospective graduate program.

If there is any advice that is always true, it would be always keep your options open.  Life is unpredictable, and choices are not necessarily irrevocable.  The funding, housing and lifestyle you have in graduate school are all important.  Happiness, whatever that means to you, is more than courses and the research lab.