Curious
Look into room 20 every day
On each day (except on day 5), before doing anything else, check out the door of apartment 20 on floor 4. (It's actually closed on Day 1, maybe you should still check it out on day 1, you never know).

New neighbor
Help Nick on the first day
Instead of entering your apartment, check out floor 3 and talk to Nick.

Worthless cook
Burn the pizza
Put the pizza in the microwave and simply let the microwave running when checking Sashas room. When you return, eat the burned pizza.

Culinary
Heat the pizza
Same as Worthless cook, but this time turn off the microwave before checking Sashas room. Eat the pizza when you return.

No Achievement on Day 2

Not efficient
Get caught in the hallway on day 3
After taking your shower, simply get caught by the woman on the hallway (instead of running back into your apartment).

Desperate
Run outdoors on day 4
When being chased by the woman, just run outside of the apartment Building. (After that you will probably get caught.)

1st ending
End up in the hospital
Just get caught by the woman on Day 4.

2nd ending
Go to jail
As soon as you get into the kitchen, take the knife from the open drawer and get towards the woman.

Always hungry student
Look into Sasha's refrigerator
As soon as you enter Sashas room, open the fridge.
(You can actually open her fridge on Day 1, but I don't think the achievement triggered for me there.)

3rd ending
Expose Sasha
Just put the figurine on Sashas table as Nick suggests.