A student wrote to me about a grade they got in my Foundations of Anthropology class (ANTH 401). This student was not happy that they received a 'C' as a grade with a 79% average since they have desires to go to graduate school. At first I was going to not reply at all since there really isn't much I can do about grades unless I've made a mistake somewhere (which was not the case here). In the end I replied with some advice. In case this will help other students, I repeat it here.
I understand your frustration with the grade - you were close - but I had to do a cut off somewhere that was consistent with everyone else. Thus, you just barely didn't make the next grade. There isn't really anything I can do to change that unless I made a math error somewhere.
If you are interested in going on to grad school, your grades are not the only thing that is going to make a difference. More important than grades are going to be (1) letters of reference (2) projects/papers/presentations that you have done (3) GREs (for most schools). Individual grades can be 'explained' in statements of purpose. The other material, however, makes a huge difference to committees reviewing materials. So here is what I suggest:
(1) start working with a faculty member who is in the area you would like to focus on for graduate school. This will help get you a good letter of recommendation. Take the initiative here -- volunteer to do some aspect of a research project that the faculty member is working. Do this work in your spare time to get the experience and background you need to be a good grad school candidate. What area are you hoping to focus on? I can direct you in the right direction - to the right person...
(2) Find out if you can turn that project into a paper or poster for a national meeting (or regional). I can help you identify a conference that would work well for that - there are many different conferences.
(3) Begin preparing for GREs now - even you are taking them in the fall. The more familiar you are with the kind of questions that the GRE consists of, the better you will do. Take a tutoring class on the GREs if necessary -- sometimes it helps to have some structure to that kind of studying since it is easy to blow off on your own.