My advice is first to make sure you diversify your list. Acceptance rates to top tier schools are under 5% and the trend is to keep droping every year as more students apply annually. In my case I did the economics major with minors in math, polisci, French, and Chinese (did a semester in Shanghai and the other in Paris). The math major is good, but make sure that you take those classes that are relevant over those not so much. Minimum requirements are Intro to Stats, Cal I-III, Linear Algebra; good classes to take are Real Analysis, Differential Equations, Probability and Mathematical Statistics. As far as the econ classes it will really depend on your interest. If you want to do finance, focus on time series and try to present your undergrad work at a conference or published in the best of cases. Some good experiences are the Dallas Fed ESP, Fed internships, and the AEA Summer Training Program.
Once again, don't look at the programs just for the names, but the actual research faculty and candidates are taking and the culture of the program as well as the posibilities to engage in your field. If you look for finance, look for a program with a strong time-series econometrics faculty. If you like the Chicago-style (10 acepted only 2 get their PhD), go for it if not look for programs where students don't compete, but collaborate, etc.
Secure good letters of recommendation from faculty that knows you well. Lastly, make sure to take the GRE durring your junior summer since that way you can prepare for it and it will help your application.
PS: GIS training is definitly a plus as well.