Your character is the strongest key here. Different hangovers and buzzes help but the main key is to get gear that your character can work with. And that matches your playstyle.

It is tempting to go Jack Of All trades, but that leaves you VERY vulnerable to specific enemies.

For example. If you like guns you want to invest alot in SHOOT obviously. Better aim and heavier hits all in one. Or if your a brawler, you want ARMOUR and HIT. Armour speaks for itself as you will be charging in. And if you just want to avoid firefights all together, Then you can try good SNEAK and high OBLIT (Mostly so you can just frag rooms without entering them yourself)

Your minimap wil be your best friend out there. Mostly as it will reveal to you if you are anywhere near the exit. Normal doors will be the red lines on the map. The exit will be the green one. Note that the minimap can see through walls unlike you. So you dont even have to be in the same room as the exit to reveal it.

Also the room layout is important. Enemies are hardly ever around corridors or the bar rooms. But they will probably swarm in interior rooms or bathrooms. (Probably since Toilet Paper is a valued commodity. Dont ask me why)

Just pay attention to your minimap at all times and youll be able to stay ahead of the purifiers. (Ill get to those in the next tip)

If you stick around one floor long enough the S.O.B. purifers will come after you. When this happens you better be as far away as possible from the entrance. As that is where he will come from. He has a minigun, alot of armour and a massive reservoir of health. But the weight of all his gear will slow him down. And hes even slower when he is firing.

This can be used to your advantage. Either to outrun the purifier, or turn the tables. As he moves slowly he is very weak to explosives, or simple hit and run tactics. If you lure him into a room with two doors leading out of it you can hit him from one side and then run to the other as he tries to fire at you.

Still engaging a purifier in a corridor or out in the open is a bad idea. And should be avoided at all costs, the knockback of his attacks will destroy almost anything in his path.

If you are clever you may be able to shove a bunch of enemies between him and you. If it doesnt hurt him it will slow him down further.

Well its obvious. Keep an eye on your bar. If you get in a sticky situation it will drop fast. So you want to keep yourself topped up at all times.

Medistims are by all means the most effective means of healing. But you cant shoot yourself up too much. As long as you are "Medicated" you cant use any meds until the effect wears off.

Same goes for food. Food is more common and it heals instantly. Usually for less though. But you can cook meals that work better. Although each time you eat you become "Stuffed" for about 30 seconds. And in that period you cant eat again. And watch it. Eating things like junk food may have side effects.

You cant expect to clear the entire game with one character, when your character dies. Another wil take his place and you lose the gear and hangovers that character had. So you want to make sure you can rearm your new character with something decent. Try to stockpile weopons, meds and food at your home so if something goes wrong all isnt lost.

Also remember to stockpile a few fanny packs too. They can help alot if you can get a new character kitted out in a hurry.

That the end of the 5 tips i got for you. Hope this helps! And go get em!