These all must be done in a single playthrough:
1. [Joe] • In the mess hall, stab Hank, Gas Pipe, and Bumpy with your shiv. The scene will "reset" after each kill, but they still count, and you MUST stab all three.
2. Have Christine sleep with Dale when you first run into him (fire escape), and have Joe mess around with Chiquita (see Blown Away). It's not murder, but if you play nice you might not get the "shoot him" option at the end.
3. [Christine] • Call the mob on Mickey (see Dial M For Murder).
4. [Joe] • Kill Gas Pipe with the rock (you don't have a choice).
5. [Joe] • Push Officer Mason off the cliff (see Payback Time).
6. [Christine] • Shoot Grassi after he kills the mobster.
7. [Christine] • Shoot Joe (see Sleeping with the Fishes).

Unlocks after you leave your cell

Have Christine clean the house

Find all 5 bobby pins:
1. Christine's apartment, top dresser drawer
2. Opera dressing room, in the big trunk
3. Dressing room at Mickey's club, in the trunk on the floor
4. Vivian's bed
5. At the café, in Bernadette's purse (after you get the diary back)

Leave the apartment and re-enter 2 or 3 times. The cat will move from the bookcase to the table, then onto the record. Turn on the player to get the achievement.

Go to dinner with Grassi.

Go to Washington Square Park (after you give Sutter the valo) and click the bushes.

Give the Lucky Lager to the homeless guy in the park, then speak to him.

Unlocks after Christine tells her story to the author.

Crack the safe in Mickey's office, combine the 2 ledgers, then call the Mafia on his phone to rat him out.

Warn Bee and the mermaid about the mob's plan for Mickey.

Unlocks when you leave the yard and get offered a job.

Give Chiquita your wedding ring, then choose "ok".

At the hospital when the doctor asks if you've killed anyone, answer "yes" and bargain to stay in the infirmary. Then fix the radiator, phone, and anesthesia tank.

After fixing the anesthesia, use it on the doctor.

Open the fridge-safe on the first try. (Choose "I have no idea" until you learn the correct password.)

Unlocks when you open the safe.

Give the seagull egg to the Birdman (before the book).

Once behind Mason, click him once, then again to push him over the bridge.

Get Bernadette to watch your cat.

Unlocks when you switch back to Joe at the phone.

Get Grassi to shoot Chicago (appeal to his honor twice, then egg him on), then shoot Grassi to continue Cold Blood.
"Leave without Joe."
"Shoot Joe."
Cold Blood should unlock if you killed everyone else.

RELOAD
When Grassi and Chicago aim at each other, kick the trash can.

"Leave without Joe."
"Let him go."

RELOAD
Choice on the dock doesn't matter.
"Leave with Joe."