I kind of have the opposite advice. I did horrible on the GRE and i got in to a wonderful program at University of Michigan. However, the rest of my application was really strong - ~3 years of research, great LOR, high GPA, and first generation college student and non-traditional student.
Additional advice that I have is to contact professors as early as you can, develop good relationships with them, and keep in good contact throughout the whole process. I didn't get a chance to develop relationship at University of Oregon and i'm convinced that's why I haven't even heard from them. Do this regardless if you are going straight into a lab or on lab rotations. It will help you determine where you'd like to go and who you get along with, etc. Also, get in touch with their grad students. Ask them how their expectations have been met with their advisor and likes/dislikes about them.
Start drafting your statements early and ask profs to look them over. Also, contact the people who you'd like to write letters for you early. Remember they're super busy and need time to write a letter for you.
*ps i just realized i posted in the philosophy forum. hopefully this advice is still helpful for you guys! I saw the topic on the most recent forum!*