In your candidate guide, you will have the Leadership Traits and Leadership Principles. I think these were also a question or two on one of the academic test, but these two bits of knowledge are widely acceptable to know before OCS, so I'm a-ok putting them here.
A guide to Leadership Traits and Principles can be found here.
LEADERSHIP TRAITS
These are single words, and they can be remembered with the acronym JJ-DID-TIE-BUCKLE. The page I linked has the definitions and significance. You don't need to memorize those, but you should have a good idea what they mean, because you will use these traits when evaluating your peers. Definitely memorize the traits. They don't have to go in any order, but it's easy to stick to tying buckles.
Justice
Judgement
Dependability
Integrity
Decisiveness
Tact
Initiative
Enthusiasm
Bearing
Unselfishness
Courage
Knowledge
Loyalty
Endurance
The trait that will be beat into your head at OCS is integrity. When you write peer evaluations, you will assign three positive and three negative traits to your peers. Sometimes when people can't think of any negative traits of a peer, they just randomly pick a trait to put down. For the love of god, do NOT say a candidate lacks integrity unless you have a specific incident in which your peer lacked integrity. I was pretty soft in my peer evaluations because I feel like everyone has their struggles and I'm not in a place to blast someone if I'm just a candidate. If I truly couldn't think of bad things to say about someone, but if I knew someone failed a test, I would list Knowledge as a negative trait and list a test failure as the reason. I'm giving the instructors nothing new about this person, and I'm not undermining their character. Endurance and Enthusiasm were also safe negative throwaways. Everyone has moments where they can be stronger and everyone certainly has moments where they can be more thrilled to crawl through icy, muddy water.