Tilt the left stick a little to move slowly and all the way to move quickly.
The faster you move, the easier it will be for enemies to spot you.
The lower your stance, the less likely it is that you will be spotted.
Use the left stick to move in any stance.
Aiming from cover
Approach an object to stick to it and conceal yourself.
You can even move along the object while staying hidden.
While behind cover, hold the Ready Weapon button to pop out and take aim (only if the cover allows).
Release the button to return to cover.
Lean over a cliff edge or other ledge to grab and hang off it.
Use the left stick to move while hanging.
Climb back up with the button.
Let go and drop down with the button.
Hanging
Enemies that spot you will notify their allies by shouting, calling on the radio, or other means.
Take the appropriate action for the situation, such as eliminating the enemy, fleeing, or hiding.
If a battle is underway, reinforcements might still show up even after you eliminate the initial enemy.
If you give enemies the slip, they will spend time carefully searching the area where they last saw you.
Perform a quick dive in the the direction you are tilting the left stick.
This is useful for evading enemy attacks or their line of sight.