That sounds probably easier than it actually is.
Selecting the right school might be a little bit more complicated than choosing your undergrad institution, since the US has a large number of schools offering Phd programs in Economics, spreading from the worlds top schools to schools you should completely forget. Other factors are large differences in environment (think New York City and deep deep Midwest) and the cost for the whole process.
The first question is how competitive are you with your background? Are you lone top of your class, years of research assistance, Studienstiftler (for Germans…), publications, a lot of math courses, then hey shoot for the top 5, otherwise be a little bit more cautious. Ok if your grades are pretty good, you have a nice Masters thesis, good standing with senior faculty, but especially a good quantitative background, you can look lets say somewhere within the 20 or 30 highest ranked schools (always include some top-schools, since there is a certain degree of randomness in the admissions procedure involved) .
There are various sources for these places, http://home.comcast.net/~chrissilvey/ gives a good overview about the various rankings. www.econphd.net also has some.
So get, lets say the top thirty schools, cancel those, where you would never go due to environment conditions, like too hot in South California or too much snow in Minnesota. Then consider whether you have a strong research interest like say, Trade theory or Labor economics, check which schools have faculty working on that. Usually the higher the schools are in the rankings, the more likely they will cover all fields. But one word of warning, most students arrive with a certain idea about specializing but will change that during their first two years, and honestly, after they admitted you, nobody will care what you claimed in your personal statement.
For the rest start with their website, see what kind of feeling you have about the place, talk with professors at your home institution whether they have recommendations (especially with those who studied or worked in the US), scout other websites and internet forums, if you have questions, e-mail departments or current grad students (like me ;-). Surely some of them won't respond, but I guess most will answer your questions (as long as you don't have five pages of them and they actually can answer them). Also money plays role, most schools give a certain degree of Financial aid, usually the higher ranked the school is, the more money you get. Financial aid is usually merit-based and not need-based, so you might get offers without a stipend. Have some thoughts whether you still want to go in that case and how you finance it. Again current students, departments and their websites are sources for this kind of information.
At the end you should have a list with say 7to 15 Schools, about which you feel confident that you would accept an admission. (otherwise what's the reason for applying…)
A lot of admission guides mention safety schools. This indicates a school, where you are quite sure of getting accepted. If you are really determined about getting a PhD, then you should include at least one, better two.
Now here you have to ask yourself another question, does it have to be the US? If you can imagine staying in Europe, you can find a certain number of Departments with Grad schools which are competitive with schools say starting around rank 15 to 30 in the US. Names are LSE, UCL, Toulouse, Tinbergen (Amsterdam & Rotterdam), Tilburg, Barcelona, etc… (check out the rankings at Econphd.net, you can find the good schools in Europe, especially in the subfield rankings).
They also work fine as safety schools, since most of their deadlines are after you get notice from the US. (this is not a guarantee, some schools may actually have earlier deadlines….).