What are the training resources for promotion boards?

PV2 Sterger, the best thing you can do for yourself is read, read, and read some more. As SFC Squires said, develop your reasoning skills and figure it out. But since you asked, and few Soldiers have the motivation to go even that far, here is a baseline to start with:
The Soldiers manual of common tasks and maintenance as previously noted
The Soldiers guide
Soldiers Creed/Code of Conduct
Chain of command
Army customs/couresies
Drill and ceremony
Wear and appearance of military uniforms (AR 670-1 and DA PAM 670-1)
Physical readiness training
Army Body Composition Program
Map reading / land navigation
Survival, maintenance, first aid/TCCC
Uniform Code of Military Justice
awards and decorations
Training units and developing leaders

These are among the most common MOS-immaterial topics taught and tested in the army. It can be overwhelming at first, but make an effort to read and study a little bit each day. These will give you the basic guidelines of how to Soldier, regardless of your job.

In addition to that, go to the Army Career Tracker and ArmyFit websites online. Dig around and look at the tools you can use to assess your current fitness and plan your career. Finally, find a mentor but always develop yourself.

CPT Gabe Snell Hit the nail on the head. You mentioned in your response stuff like Soldiers Creed. I bet you would have found that on line. Apply some reasoning skills to a basic internet search and you will likely find yourself answering your own question.

Having said that, get to know the Soldier's Manual of Common Tasks very well. Generally, the junior enlisted ranks should really own those tasks. You are the ones that the senior leaders are expecting to do those things. I am not saying that most NCO's that are worth a shit don't also know the basic skills, but in my experience, the E2 3 and 4s are much more intimately familiar with them.

Know your equipment well, especially your vehicle and your commo. If your leadership learns that PV2 Sterger's stuff is always maintained and reliable, it will go a long way towards your recognition and advancement