Just finished the game and had the same question! Fortunately, it turns out some awesome person has made a quite comprehensive wiki for the game, including a page listing all the endings.
Here's a short version of how to get them:
Good Ending & Bad End #2 Play the game normally until you get to the final choice. Selecting "Go" gives the good end, "Stay" gives the bad. (If you pick up the doll in the kitchen on day 4 and then get the good end, you'll get a little secret room after the credits.)
Bad End #1 On day 3, leave the house once as normal. Then after reentering, leave the house again and walk to the end of the pathway.
Worst End On day 4, enter the kitchen and interact with the doll on the floor. When asked if you want to take it with you, select "No". Then continue as normal to the parents' room.
