Y'all
Recently joined this site, but have stayed quiet in the background. Studied only for OAR, as my interest is Navy Intel; have obtained HPSP but am exploring other ways to serve. Took test, earned a 58. Background is BS in Neuroscience (with pre-medical requisite classes covered) and MS in Forensic Science. Figured I'd contribute, as this site helped a great deal and my score is something to be content with.
Math - Hardest section, unsure if bc poor math skills or actually difficult. Most questions were rate-related, proportions, or work hour. Maybe one or two math riddles, and one log question (can't remember the details, as it seemed too complex to me and I skipped nearly immediately). I felt like I was getting answers right since the questions got harder and harder, but like my brain was working through molasses. I would argue to study this section in two ways: first, make sure you are comfortable with most topics from whatever study source you use. Once you feel you have it down cold, start timing yourself. I did not do that, and greatly suffered for it, as my pacing was abysmal. Scour kahn academy for algebra I & II topics, and try to practice shortcuts (simplifying fractions, recognizing certain triangle values, root values, etc) to expedite things along.
Reading - Not terribly difficult if you really grasp critical thinking. Another poster noted elimination is key here, and I would say elimination may be what makes or breaks you here. Nearly every passage had the answer theme of 2 clearly wrong answers (the wrong subject was doing the action of the passage, or just utter nonsense) and an answer that was close but not quite (usually copying a word from the passage like a buzzword to drag you off course). Recognize the garbage outright, which gives you an immediate 50/50 shot; afterwards, be wary of an answer that directly copies a phrase or word verbatim. Just because those words are there doesn't make it right. Try to practice by reading articles of random themes, especially things you don't regularly read, and try to rephrase them into your own words and reduce the amount of jargon. Many passages seemed like they were directions or from rule books, and these sources may be best to practice from.
Mech Comp - Extremely weird in my opinion. Only had kinematics, simple machines, mech energy and fluids (but only gases, not liquids); actually saw the ideal gas law, but didn't think I would. No electronics, magnetism. No calcuations whatsoever except for the ideal gas law (I had to write it down and play with variables a tiny bit). Questions were super basic conceptual issues. If you are still in college, please try to take physics (a non-calculus based one is totally cool) so that this section becomes a walk in the park. If not an option or have tried and found it to be extremely difficult, I would not worry, as every one of these concepts is also on kahn academy. Again, concepts were important; if you understand and know the equations, bonus points, but just understand when acceleration is constant, how a pulley works, etc.
As an extra tip, you do have small amounts of time between each section. TAKE ADVANTAGE OF THIS BREAK. Whether you just got murdered by math or just tore it up because you have great big brain energy, take breathers where you can get one. Try to relax, take some slow breaths, let out a quiet expletive - whatever it takes for you to shake off the last section and move on to the next one.
As for sources, that post on pg 257 (the godsend post as it is saved on my desktop) has great math practice. I personally used the momentix study prep materials, which were alright; math was way too easy, but the reading and mech prep was pretty in depth. Lastly, I'll post a study guide I found that had pretty grueling but very effective practice problems. Word of warning; it may be a repost.
I wish you all good luck as your test dates approach!