By adding context-sensitive controls and limiting most of your action to the triangle button. Walk up to a wall, an on-screen icon will show that Snake can sidle up against it. Approach a dumpster, the icon will change to show that Snake can get in. To aim, simply press L1. To fire, L2. Holding L1 then pressing triangle will bring your view to first person mode.
While the new first person mode is handy in many situations, only expert level players will have the skill and patience to play the entire game in this fashion. It's fantastic for taking out PMCs and surveying your surroundings. Any encounter that involves the game's close quarters combat, however, will pull you back in third-person. Still, for those who want to play the game through again with the intention of never being spotted may be up to the challenge.
Back to the controls, the X button changes Snake's stance. Tap it and he'll hunch over. Snake can still move around easily in this stance, keeping cover below certain objects and below the sight line of windows. Hold X a moment longer and Snake will lay down, entering the prone position and allowing him to crawl for extra stealth. This is the stance with which you'll obtain the highest level of cover and the one that will allow you to do the "inchworm", Snake's breakdancing, slow moving forward progression. During these times, you'll know exactly how well-covered you are, as your camouflage percentage is always shown in the HUD at the top right.