Here are the choices you need to make in order to get this achievement :
*** Spoiler - click to reveal ***
--The first choice doesn't matter
DAY 1--------------------------------------------------------------------------------------
Do not reply
Do nothing
Do not attempt to take the cutlet
--It doesn't matter if you take the keys or not
Keep silent
DAY 2--------------------------------------------------------------------------------------
Map: Go to infirmary, clubhouse, library and music club
Go alone
Bet with Alisa
--If you want the good ending with Alisa, you have to win against her (it gives "many points"), if not lose against her
Map: Go to Genda Square or to the beach
DAY 3--------------------------------------------------------------------------------------
Fine, wait a minute
You know, Olga asked me to help her tonight...
I should go take a look
Okay I'll come
--The next choice doesn't matter
Make up another excuse
DAY 4--------------------------------------------------------------------------------------
Map: Go to the Boat-house and then to the forest
Just asking...
Overdose of stolen candies, right?
Ask about the bundle
Give Alisa the activated carbon
--It doesn't matter if you eat the apple or not
Go with Alisa
--Choose any combination of directions
DAY 5--------------------------------------------------------------------------------------
Map: Go to infirmary
--It doesn't matter with who you go collect the strawberries
Yep, I tried my best!
Map: Go to the library
Stay on guard
Map: Go anywhere you want
Try to find out what Alisa and Lena are arguing about