What whaaat!
After playing this game for a week, I learned today that there is a cover system if you play in first person.
When you go close up to wall, you've noticed your gun will be lowered, use you left trigger (RMB) to then peek out!
While I appreciate Bethesda intentionally not showing or talking about the game prior to the launch, I feel like things like this are totally imperative to how you play the game!
Feel free to post other obvious but not so obvious things you have found. No spoilers though.