Everything you stated above will help you in applying for grad school, but it depends which program you want to go to and what type of studies you plan for.
Different schools have slightly different requirements, but overall and on average, graduate programs in the sciences look for a strong academic background and research experience. This shows the school that you could not only get through the PhD program, but be a successful student with class as well as research.
The GRE exams are also important, but neither of the three "basic" requirements is enough. Good grades are helpful, good GRE score is helpful, and a good set of recommendation letters and personal statement is helpful. You could get into a program even if one of those is not "perfect", but if you show you are well-rounded and successful in all three, you have an excellent chance of getting accepted.
As a general rule, I'd recommend you make a list of your top 5 schools you want to apply to, and check the details in their application process. Some departments look for different types of candidates, and put emphasis on things like "extra curricular activities" or your personal statement. The best advice is to do your research, and know what each of the departments is looking for.
Don't give up on your grades! You'll have a much greater chance of getting accepted if you put such effort in your studies.
Good luck!