To make it in academia, you have to produce research -- conference papers, journal papers, grant applications, maybe even books (depends on your field). Demonstrating intelligence in the form of good grades and high GRE/GMAT scores is important for getting into a PhD program, but to actually finish, you need to be able to stick to a difficult multi-year project and finish it. There are many "ABDs" in the world. These are people who had the intelligence to do the PhD "all but dissertation" but didn't have the persistence to finish the dissertation.
I am a new faculty member and not yet working with PhDs, but if they put me in charge of PhD admissions, I think the number one indicator that a candidate could succeed would be "did they do a masters thesis?" and the number one indicator of whether they could handle a research masters would be "did they do an undergrad honors thesis?".
So my suggestion is, work hard to get straight A's, but also make a point of doing research projects. That might mean joining your school's honors program, or doing independent study courses, or working as a research assistant for a professor. Get your name on some published research, and (this is important) make sure you have an advisor (or two) who are active in their fields and who will be known to professors on the admissions committee at schools you'll apply to.
I am a new faculty member and not yet working with PhDs, but if they put me in charge of PhD admissions, I think the number one indicator that a candidate could succeed would be "did they do a masters thesis?" and the number one indicator of whether they could handle a research masters would be "did they do an undergrad honors thesis?".
So my suggestion is, work hard to get straight A's, but also make a point of doing research projects. That might mean joining your school's honors program, or doing independent study courses, or working as a research assistant for a professor. Get your name on some published research, and (this is important) make sure you have an advisor (or two) who are active in their fields and who will be known to professors on the admissions committee at schools you'll apply to.