I wish I had known that MCAT competency is based on BOTH science aptitude AND the ability to unpack question stems. It wasn't until studying for my retake that I started scoring well (read: mid-high 30s). The difference between low 30s and high 30s is, literally, only a handful of questions; being able to interpret EXACTLY what is being asked is absolutely critical.
Also, I was given the opportunity to teach someone for a few weeks prior to my exam. If a friend asks you to help them go over a full-length, to assist them in understanding what they missed, DO IT.