I completely agree with
@ActinicKeratosis. Haven't gotten my score (and did not feel good afterwards cause I did make a lot of dumb mistakes lol) but when I was scoring in the 250's, it really didn't come down to more knowledge, per se, but making sure I didn't misread or jump too quickly to an answer. Obviously it still happens time to time but that's what pushed me from low 250's to getting into the 260's and even 270's consistently for my last 5 practice tests. And when I would review them, I definitely noticed that I was making a lot fewer "silly" mistakes.
On that, one thing I did in particular was cross out each answer choice for each question. This way, for example, if I wanted to selected Mycoplasma and accidently quickly selected Mycobacterium marinum because I just glanced and saw "Myco-" it would force me to quickly glance at each answer choice to strike it out and it took maybe 5-10 extra seconds but definitely saved me a few times on the NBME's.