This section tells you all the requirements to get all characters.
Frank: Win one game
Chuck: Collect 10 tapes
Richard: Win on Kvitoya
Hannah: Collect 20 tapes
Rafaella: Win on Normal
Sylvia: Collect 30 tapes
Invis. Man: Win on Hard
Invis. Woman: Win on Nightmare
Jack: Win five games
Adele: Win on Saint-Martin
Oliver: Win on Bunker 51
Katya: Win on Founder's Hall
Omar: Win on Chateau
Alex: Win on Isla Grande
Johan: Win 10 games
Susanna: Collect 50 tapes

Secret Achievements:
100% death proof: Win a 4 player online game with 4 survivors.
Spiders are scary: Pause while viewing a statue or the White Noise.
Murder is easy: Die after collecting exactly 7 tapes.

Normal Achievements:
Audiophile: Collect 100 tapes.
Audiophage: Collect 200 tapes.
Fear no evil: Win a game with four players.
Hello?: Finish an online game (as far as i can tell, you have to have four players in-game for a game to count).
I'll be right back!: Finish 5 online games.
Who's There!: Finish 10 online games.
You may not survive: Finish 20 online games.
Resist the beast: Win on nightmare difficulty.
Clock tower: Win a game in less than 6 minutes on at least normal difficulty.
Children of the Night: Unlock all characters.
Urban legend: Win an online game (with four players) as the last one alive.
Never explain anything: Walk 42,195 meters total.
Who you gonna call?: Win an online game with the default characters (Kurt, Jean Luc, Anne Marie, and Sarah).
Self-torture: Win a game without running.
No tears, please: Win an online game without picking up a tape.
Appointment with death: Have everyone in a game (with four people) die.
Sixth sense: Finish an online game with 4 female characters.
The charm of horror: Win a 4-player game with each player picking up two tapes.

Characters:

For those you need to pick up tapes to unlock (Chuck, Hannah, Sylvia, Alisa, Susanna): Play a bunch of single-player games and pick up as many tapes as possible in each. If you manage to beat a map while doing this then you just hit two birds with one stone.

For those you need to beat maps to unlock: (Richard, Adele, Oliver, Katya, Omar, Alex): Play online games with as many people as possible (to increase your odds of winning).

For those you need to win a certain amount of games to unlock (Frank, Jack, Johan): You should do this while unlocking the other characters, but follow the same strategy as the ones you beat maps to unlock (except play on only one map so you can get all the spawns and stuff on the map down and make it easier).

For those you need to beat a game on a certain difficulty for (Rafella, Invisible Man, Invisible Woman): Use the same strategy as the last one.

Achievements:

Audiophile/Audiophage: Use the same strategy as you used for unlocking the characters that require picking up tapes.

Fear no evil: Get four people together (either friends or people from the forum) and play on easy mode, and work as hard as humanly possible to win.

Hello?/I'll Be right back!/Who's There!/You may not survive: Play a ♥♥♥♥♥♥♥ of games with the previously mentioned four people.

Resist the beast: Get those four people together once more and win a game on nightmare. Not much of a strategy except do it as fast as possible and make sure at least one person has eyes on him (so he doesn't move).

Clock Tower: Get your four people together and speedily complete a game on normal. It helps if you have all characters unlocked as everyone has a specific play style and having all characters helps some people play better.

Children of the night: Follow the "Characters" portion of the "Stratagies" section.

Urban Legend: Sacrifice your fellow players in an online game and pick up the last tape.

Never explain anything: Play a single-player game on easy mode (while your posse of players is still pissed at you for making them die) and walk around a lot. Easiest on outside maps. Note: While unlocking everythign else, you may earn this achievement, but it depends on how much walking you did while playing.

Who you gonna call: Now that your squad of survivors is cooled off, have everyone play as the original four characters (Kurt, Jean Luc, Anne Marie, and Sarah) in an easy mode round and win.

Self-torture: Start an onlne game in easy mode and have everyone else find tapes while you hide with your face turned towards a wall (or just dont run from the monster, but you might die in that case).

No tears, please: Be a lazy ♥♥♥♥♥♥♥ and dont do anything while your teamates do all the work.

Appointment with death: Have your group of groovy game-players all die.

Sixth Sense: Win an online game of four players on easy mode with an all-female cast.

The charm of horror: Have every player in your group pick up two tapes. It's best to play in easy mode without splitting up.

I hope you all enjoyed my guide. It's my first time making one and i don't have all of the achievements or characters unlocked myself, but i did my best to help all of you. If it did help, please rate this guide up. If you notice anything i missed or have an easier way to unlock something, please comment it and i'll update my guide. Thanks for reading, and have a great day!