I think 780 is a shaky score for a domestic student wanting to go to "Top Schools". Remember, your degree is worth what you put into your research, not necessarily the school you go to. I think your 780 will be fine for getting into places, just perhaps not the best schools. If you want a 90%+, you should have started the process of studying way before now. There really is no trick to getting over a 90% with this little time left to study.