NG+ changes the game significantly by making every enemy an extremely lethal threat - at least for the first level. It compensates for this by increasing the amount of money you earn, which allows you to snowball continuously in character upgrades. In NG+, making it past East Wing - Building C is, in my opinion, harder than the Barge.

If you have activated all three generators without fighting both mini-bosses, it is probably worth it to just leave, rather than staying to full-clear the map, though this only applies to the first level. Similarly, it is useful to recognize horde-spawning doors: usually, you will want to clear these for the extra money, but before you buy the Axe they can be fatal.

The below diagram is a great example of obvious horde doors. At doors 1 & 2, there is no space on the map for any kind of room beyond the doorway, thus meaning they must be horde doors. The horde at door 3 was activated as soon as I entered the connecting room, but there was no warning sign, as there is plenty of space for a real room to generate.
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• Camera height is dependent on the size of the room. This can be abused by standing at the doorway of rooms with a high height, and using the extra range to scout connecting rooms.
  
• Doorways in general are good places to be, both for room to maneuver and to be warned of approaching enemies.
  
• When you can't see the entirety of a room after entering, check the map. Seeing the general shape of the room and the position of connecting doors will let you know where to expect threats.
  
• You can hear doors opening and closing as enemies charge you (especially common at the start of some levels). If you hear something approaching, it's probably not the best time to search a container.

• Don't get fancy - melee kills are good, trying to kite enemies over mines is usually not. Trying to get value from the godforsaken laser traps is never good.
  
• Get comfortable rolling and conserving sprint.
  
• Use a drone to clear that space in the inventory.
  
• Don't buy guns before searching the area, unless it's an emergency.
  
• Plates are rarer than health, so if you have an abundance of medkits, it can be smarter to save plates rather than using them immediately.

You can spawn with better-than-usual starting gear on NG+, and it can be worth it to aim for a good roll. The only "bad" rolls are probably the shotgun and the light energy rifle (the fire delay will kill you).

Here's an example of an optimal outcome from level one, including health upgrades and enough money to buy the shield:
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The sole advantage you have in NG+ is that YOU GET MORE MONEY.
You will use this advantage to purchase every single upgrade you can. Funds can be limited on level one, since you should buy the axe first and ideally have enough for the shield afterwards, but try to get the Health ++ and Health + that reliably appear in the shop.

After that, your goal is to clear the upgrade station on every level. It refreshes on every level, which is why visiting Construction is an especially helpful boost. You should be able to buy most character upgrades, but in order of importance they run:

Leg Pouch (can only buy twice) > Stamina > Ranged Damage > Health > Protection > Crit > Melee

Melee won't help you one-shot basic enemies any harder, but it can be useful for easy melee mini-bosses like the hand. If you're extremely low on cash, skip it to be sure you can afford important picks next level.

These screenshots are from the end of the SSLW building. My combined max health/protection is almost 700, and I'm doing 150% the damage with 220% the stamina. This upgrade stacking is absolutely vital to beating NG+.
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Unfortunately, this is also why losing a volunteer past level one means your run is functionally over. You need the cumulative advantage of these upgrades.

The most important weapon in the game is the Axe, which should be your first purchase. Even on NG+, it can one-shot every minor enemy, and I only ever replace it with the free katana for style points. You should be comfortable with melee; swing a little bit before contact and move into the enemy at the same time. There is a damage window, and this helps ensure they don't get close enough to damage you in return.

Some weapons pierce terrain, such as the rail rifle. More terrain is pierceable than you might expect, so on crowded levels like Transport Center it can be worth testing.

Drones and turrets stack. Automatic rifle variants are the most common. Try to use them efficiently so you maintain your stacks and clear inventory space from one-offs.

Other than that, NG+ is not the place to experiment. Use what you are comfortable with. Past the first couple of levels, ammo frequently becomes a nonissue.
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• Sadly, shotguns and nailguns (my beloved) are not good in NG+
  
• The hunting rifle will get you killed. Avoid it.
  
• The semi-auto rifle is solid, and better than light smgs for ammo conservation. You will want to swap it for the SA3, which can be found as early as the Woods/Barge and is effective for most of the game.
  
• Muzi isn't great, but keep it while you stack medium ammo. You will replace it with the automatic rifle, and then the American automatic rifle or the battle rifle. I love the battle rifle in lower difficulties, where it can one-shot enemies, but for NG+ the American might be better.
  
• Get the revolver on Woods. It does insane damage and can be reloaded in stages.
  
• The Rail Rifle is decent, the Rail Gun is terrible. No slowdown and 15x the ammo cost. Don't fall for it.
  
• Start stacking energy cells after the Barge, as you will 100% want a plasma rifle.
  
• Heavy MGs can be surprisingly effective.

General tips by map:

• It's hard to dodge the laser when fighting the Eye from visual cues alone. It's easier to do it by timing - shoot with the emplacement for a while, then start walking (no need to sprint) to the other emplacement. If you get the timing down, the eye will start and finish firing the laser by the time you arrive.
  
• On Woods, you can walk through that giant water pool that spawns in the path.
  
• The Barge shouldn't be that bad. Just make sure you loot fully, since it ends suddenly.
  
• Take Construction exit after Aerospace for the bonus upgrade station/maybe katana.
  
• Go back through the double doors at the start of Transportation Center, as there is often a crate tucked closer to the level origin.
  
• The gas mask refills when not in use, but it goes down way faster in NG+. You have to stay aware of your remaining percentage, and take the time to let it refill in clear areas (just keep it equipped outside of the radiation clouds).
  
• Ditch the flashlight drone after Construction, ditch the gas mask before fighting the Transportation boss.
  
• Go to North Wing over Caves - easier environment to fight in, but whatever you do STAY OUT OF THE LASERS. They do insane damage on NG+.

In NG+, your health is in the "critical danger" zone far earlier than the flashing UI suggests. I have been one-shot from nearly 500 combined health/protection before. You will rapidly learn that there really isn't any "chip damage" anymore - it all hurts.

• Mind the slow enemies! Walking soulless can blend into blood stains and smack a chunk out of your health if you walk past them unknowingly. The radio static audio effect that plays as you approach an enemy is incredibly useful - if you start hearing it out of nowhere, immediately backtrack until you see what you were about to walk into.
  
• Enemies will respawn behind you, which is especially noticeable on Train. Enemies will almost always spawn after completing any objective, but generally just spiders and basic soulless.
  
• It feels like gun soulless have longer range on NG+, but you can still outrange them, especially on open maps like Woods. Even if the enemy is offscreen, you can generally see the damage numbers pop up if you're hitting them.
  
• Gas from the floating bacteria things only slows you and blocks your dodge, it doesn't cause damage.
  
• BEWARE of the large tentacled enemies in the lategame. The telekinetic one that roars and drops blocks like Miho isn't too bad, but the other varieties will end your run in a second. A rocket-shooting one is what took me from 500 health to 0 after I didn't notice it around a doorway, and the laser-shooting ones seem to tick for genuinely 150+ damage per second.
  
• When in doubt, activate the shield before engaging - don't just save it for moments when you're about to be hit for certain.
  
• Drones and turrets are extremely helpful for bosses, obviously.

And that's it! It will probably still take a few tries, but you're all equipped to tackle NG+, hopefully with fewer painful lessons to learn along the way. Empty Shell is a great, underplayed game, and it motivated me to write this, my first ever Steam guide - so I hope you found it useful.

Good luck, and don't give up!