All these achievements are gained by just doing the story and can't be missed.

War of the Clubs
Complete Chapter 1


PSI Snowball
Complete Chapter 2


Best Spirit Week Ever
Complete Chapter 3


Gone the Way of Disco
Complete Chapter 4


The Gift of Mystery
Complete Winter Break


Identity Crisis
Complete Chapter 5


Party in the Club
Unlock every party member


The Ultimate Club?
Completed Chapter 6


You Are More Than Your Club
Identified those who had lost their identity


Empathy
Completed Chapter 7

Just Kitten Around
Read every cat joke in the calendar
You must examine the cat calendar (in the back of the club room) every time there's a day change (so when there's a new chapter/intermission). It'll unlock after you examine the cat calendar in the credits scene.

Fan Favorite
Used the same villain in all of Alicia's adventures
After Alicia writes her first campaign, just choose to use the same villain for the rest. This will unlock after you finish the last member's campaign.

It's Not Spying, It's Scouting
Spied on every club
Make sure to spy on every club

Two Thousand Words
Drew two different posters for different occasions
If you're going to spy on every club, you'll get this achievement

Extra Cheesy
Wrote an essay with pizza on the brain
When you have to write an essay, pizza options will pop up. Just pick those.

Shock Tactics
Dealt 20 damage or more in a single turn
This is pretty easy to do, just keep in mind which characters you have and try to set up the field for maximum damage

See? Psychomancers are OP
Confused 5 enemies in a single turn
Either set up your enemies so confuse will chain or wait until a later story fight that confuse will let you get all medals.

Q: Are We Not Helping?
Convinced Baphomet to KO another New Wave Appreciation Club member
Basically just injure the closest member to Baphomet (preferably with Jacob so you can kick him closer to her) and then confuse Baphomet.

More Tactics = Better Tactics
Used three Tactics Powers in a single turn
Just hold off until you have a full tactics bar and activate everyone's tactic power.

Classing it Up
Unlock a Specialization
After the intermission, you'll unlock an extra equipment slot and specialization. If you equip two items that fall under the same category, that specialization will unlock.

Puzzle Challenger
Completed every character's Crucible Battle
Make sure to complete all challenge battles before the point of no return

Puzzle Champion
Completed every character's Mastery Battle
Make sure to complete all challenge battles before the point of no return

Queen of Clubs
Completed all side quests helping Tactics Club Members
Make sure to complete all side quests as you go and before the point of no return

Woman of the People
Completed all side quests helping students outside of the Tactics Club
Make sure to complete all side quests as you go and before the point of no return

Dragon's Hoard
Collected every upgrade
If you're already doing all challenge battles and side quests, you'll unlock this after your last side quest/challenge.

The Ultimate Tactician
Got S Rank or better in every battle
Just get all medals in all battles up to the point of no return. There is a guide in the making for how to get all medals, but if you're missing medals in certain categories, you can replay it and try to just get those and they'll be added in like you did it in one try (ex if you got all but tactical medals, you can stall the battle so you can get the min tactical attacks in and still have it registered as 8/8 medals).

Tactical Espionage Action
Snuck past the foes you don't need to face
Just walk around the cloaked figures and not in front of them. If you get caught, reload your previous save.

Man of Few Words
Heard Armando speak
Armando will talk around the time when the Principal calls you in for a meeting towards the end.

Totally Called It
Discovered which character had been dead the whole time
If you talk to everyone in the credits scene, you'll unlock this one.

Congratz, you got all (or most) of the achievements! I hope you enjoyed Wintermoor Tactics Club as much as I did.