i wanna go to usa to study phd

A PhD is a ver serious thing, unless you did an honours bachelor degree and youre going straight into your PhD studies the GRE is a must.

GRE is a must,so is toefl.Your GPA is also important.your paper your tutor. .

Not only GRE but also some english language test like IELTS/TOEFL and your previous academic scores play a major role. good luck!

I am working on my PhD degree in Japan. In fact, i think it depends on what project/field you are interested with, before you make your decision to go for a phd in the states. For my case, i fond of technology, Germany and Japan would serve me with their strenghs in technology. By the way, if you plan to hav your postdoc after PhD, also in the states, the salary they offer is quite incompentent for the time being.