Just a peace of advice a month after getting my score (I'm the foolish person that is annoyed at getting a 261 because shelf scores were a lot higher in terms of percentile and so were u world assessment scores) and reflecting a lot:
1. U World is a must, but so is paying attention during clinical rotations. There were questions that were really straightforward that I got wrong because I just didn't pay close enough attention. It's the type of stuff that isn't felt necessary to add to textbooks or doesn't sound tricky enough to make for a "good" question, so U World doesn't include it.
2. Reading Uptodate throughout your 3rd year during the day, when writing notes or just looking up management for patients, is important. It really helps you fill in the gap on stuff like atypical presentations and newly approved treatments. Some questions I got were straightforward but just little things U World missed. Also, U World doesn't necessarily have every single nuance of every single even common EKG or X-Ray finding. Some of the exam is just literally testing, if you saw something common, that UWorld doesn't emphasize. I think the NBME writers are familiar with U World, very familiar actually, and try to find holes to see who was actually paying attention on wards and not just relying on test banks.
3. I would REALLY focus on deficits of your clinical education. I didn't do very much outpatient IM at all! The consequence was that a lot of very easy management questions for outpatient IM, well I got them wrong. They were straightforward, probably so much so U World didn't think it was worth to make a question on them, but they required you to have seen the scenario or at least have read about it. I guessed some right and even initially reverse rationalized how I used "logic." In reality, many of the choices look theoretically sound but only one is standard of care, often due to the result of a trial where a strong correlation for morbidity and mortality was found but the causative pathophysiological mechanism has not yet been elucidated. For me personally, as much as the current dogma is "NO TEXTBOOKS FOR DEDICATED," there would have been benefit to reading about management for a lot of more outpatient stuff and even some inpatient nuance in STEPUP2Medicine, at least for high yield systems like cardio, renal, GI, pulm, and endo.