Sneaking

The game will require you to do a bunch of varied tasks ranging from infiltrating a hostile territory and sabotaging or stealing things, kill key targets, or simply take over the place and get rid of enemies. There are many ways of achieving this: one is doing it shooter style; with guns blazing and knocking on the enemy's door. Some may prefer the sniper approach, by whittling down the outer guards with the help of a handful of sniper rifles in the game. The most satisfying and intense however in my opinion is infiltrating the enemy base and using stealth to kill them and achieve your goals.

Stealth

The game's not a stealth game so don't expect anything special with the stealth mechanics. It is still solid however, as you can rely entirely on your patience, creativity, and exploiting the game's limitations. Stealth is activated as soon as you crouch. The game calls it "Stalking" but for easier reference, let's just use the terms interchangeably.

Stealth kills is a good way of whittling down the enemy numbers without stirring the hornet’s nest. However, to make the most of this, always wiretap all the junction boxes you find. That way, your intel view will be much more effective, revealing the enemy positions real time even if they’re behind walls or floors. This is also a good way to move deeper into enemy lines and take out the pesky sentries who can call in reinforcements if alerted. You don’t need to go full stealth all the time.

If you can achieve your goal with guns blazing, go ahead with it since it’s a lot faster. Sometimes, you can also catch groups of enemies completely unaware so using a molotov or grenade can take them all out in one go. Also, there's a specific thrown weapon called a Screaming Zemi that will make the enemies search the spot where you threw it. This is a good weapon to use if you want the enemy to break formation or if you're having problems passing through a particular spot without getting seen.

For larger targets that has a ton of hostiles roaming around, a combination of both stealth and gunfight is the best way to do it.

Enemy awareness

If you’re within the enemy’s line of sight, there will be an indicator that will appear on screen. If it fully forms into an arc, the enemy who saw you will take the necessary action depending on the zone you’re in. (See below) Use the indicator to know if the enemy has been alerted or you’re if he can see you. Sometimes however, you can deliberately let you seen fully by an enemy, especially in trespassing zones since they’ll just approach you and shoo you away. This is a good way in scoring a stealth kill as long as you do it away from the other enemies’ view.

Luring an enemy

As long you’re in crouching, you can move freely without getting the attention of nearby enemies. Now here’s how the game fails in applying this mechanic effectively. Even if you make noise, like breaking bottles or knocking down objects as you move, even if the noise is supposedly audible enough to get a person’s attention, the enemy won’t notice you, as long as you’re not within his line of sight. This also applies even if you move really fast that your footsteps are really loud. Use this advantage in sneaking from behind and taking out the enemy quickly.

Zones

If you’re just trespassing, the enemy will try to drive you away. If you didn’t leave, he will become aggressive and attack you. If you’re in hostile zones, enemies will enter Combat mode if you’re spotted and they’ll be shooting at you without warning. Take note that brandishing your weapon while trespassing will also make the enemies enter combat mode since you’re obviously a threat.

Whistling

Whistling is the way to get an enemy’s attention and lure them into an ambush. If there are two enemies near each other and both heard the whistle, only one of them will investigate the area where it came from, making it a very effective way of getting clearing your path while thinning the enemy numbers.

Takedowns

Lincoln can take down opponents in lethal and non-lethal ways. You can toggle this option in the game options. You can take down enemies while sneaking, while in cover or even when in front of them. Takedowns are instant finishers and great for whittling down enemy numbers without alerting anyone. If another enemy is close enough when you ambush another target, he’ll be stunned briefly and fall to the ground in surprise. This will give you a brief moment to execute them as well.

Furthermore, you can perform a tackle takedown to prevent an enemy from reporting your position. Basically, you need to run and press the melee button at the right time for Lincoln to tackle the enemy to the ground.

If an enemy sees you execute his ally from afar, your stealth cover will broken and you either have to engage in a firefight or relocate and lay another ambush. Supposedly enemies take the same path so it’s possible to clear an area when enemies are in search mode by ambushing them one by one in the same spot.

Run, tackle, hide.

Hiding bodies

Taken down enemies can be relocated by picking them up and placing them in inconspicuous areas like behind vegetation, furniture, dark corner etc. This will prevent arousing suspicion to enemies and trigger an area-wide search. However sometimes, you can liberately place a body within a roving enemy’s path so when they check the body, they’ll be distracted by it and you can move in for the kill.

Holstering weapons

Accidentally firing your weapon or approaching an enemy-controlled area can break your stealth approach. That said, always hide your weapons, unless you’re using a silenced version.

Silenced Weapons

As you progress in the game and provide more rackets and districts to your underbosses, you’ll unlock more weapons and shop items. You can get these silenced weapons for free in the weapon shop. For example, the silenced pistol is unlocked by increasing your favor with Vito.

Silenced weapons change the flow of your stealth approach entirely. Instead of getting up close and having increased risk of being discovered, you can now take down enemies instantly from a comfortable distance as long as you target the head. This is why weapon accuracy and stability should be acquired as soon as possible. With these upgrades, your silenced weapons will be very deadly while concealing your presence as well.

Silent Entry or Kicking Doors

If you encounter a locked door when infiltrating, you always have two options; either kick the door open or break the lock with your crowbar. Kicking the door will be the quickest way to open the door but you’ll alert anyone nearby. Breaking the lock will take a few seconds but will ensure complete silent entry.