Here is an incomplete guide for the Halloween party as far as I have unlocked them. This is by memory so if I make a mistake, please correct me
I will go by order of achievements (you can access those in the main menu).
But first some general stuff:
-1 The party is made up of 4 parts (arrival, before dancing, dancing and after dancing)
-2 To unlock alcohol in the first part, talk to the twins in the bathroom, check the closet thing on the wall to get the make-up, talk to the twins again. Go to the kitchen and talk to Lily and Hailey. Talk to them again and answer vodka-orange. Now you can get the alcohol.
-3 To unlock the pizza you need to get rid of Lily and Hailey as mentioned above. Go to the study and talk to Seth and Vicky. Go back to the kitchen and talk to Iris and Mayo twice and tell them about Seth and Vickey. The pizza is now unlocked.
-4 To get Charlotte and Chanise out of the bedroom (before dancing) talk to Bill, ask about Chanise. Tell him to get rid of them or get beer and talk to Charlotte and Chanise. (I'm not sure at the moment if there is a significant diffrence between the 2 ways of getting rid of them)
Now you can get the dildo out of the nightstand.
-5 To get rid of Vicky and Mayo in the study (before dancing) just tell them to go away. You won't be able to give Alice a drink after this so make sure you do this beforehand if Alice needs 2 drinks.
- Alice drinks Vodka lemon (once during arrival and once before dancing (before getting rid of Iris and Mayo from the study)
- Emily drinks beer by adding salt to the pizza during arrival.
- Iris drinks Booze after asking Karly and Christy what she likes after dancing.
- Mayo drinks Rum-Coca after asking Karly and Chritsy what she likes after dancing.
- Karly and Christy drink Rum-Coca before dancing.
- Seth and Vicky drink Booze before dancing.
- The twins drink Vodka Lemon before dancing
Achievements
- What is a dildo?
Make sure Alice has had 2 drinks. Talk to Ako in the kitchen about Alice. Get the dildo and hide it in the study behind the couch. Talk to Ako about Alice again. During the dancing, dance with Alice and Ako. Follow Alice and Ako for the scene.
- Cozy bathroom
Just dance with Alice and follow her alone.
- Nothing better than home
Make sure Alice has had 2 drinks. After the party go home with Alice and don't fuck the other girl in the park. You can now send Alice away and fuck Mimi or send Mimi away and fuck Alice.
- Sharing Alice
Do the above but fuck the other girl in the park.
- I want my award!
After the "What is a dildo?" event, do talk to Ako and ask for the reward.
- Just think I'm Alice
Do the same as "What is a dildo?" but make sure Alice only had one (or no?) drink(s). After the scene with Alice and Ako, go talk to Ako in the study.
-Bill x Iris
Only possible if you date Mayo. Talk to Bill before dancing. Talk to iris and Mayo in the study and ask them about Bill. Dance with Bill during dancing. Give Iris a drink. After dancing talk about dancing to Bill and then talk to him again and choose the option to help him have sex.
- Bill x Mayo
The same as above but only possible when you date Iris. And you give Mayo the drink instead of Iris ofcourse.
- One for you, One for me
Again, the same as above but now you have to talk to the twins about Bill and give them a drink.
- Kinky bottle game
During the dancing go outside a play the game. Make sure Emily, the Twins, Mayo and Iris had their drinks (I assume this is important, but have not tested if it works without all the drinks).
Make sure the twins have not left the party (this happens if you have sex with them with Bill). After the party, choose to continue the bottle game.
- Fucking pervert!
I have not yet unlocked this one.
- Midnight swim
Talk to Iris and Lily before the dancing. Ask them about the jacuzzi. (you need to get Iris and Mayo out of the study first.)
Make sure Iris, Lily and Emily had their drinks. After the party choose the jacuzzi option.
- No tool? Use your tongue!
Give Karly and Christy their drinks and dance with them. Follow them (make sure the dildo is not hidden in the bed.)
- A tool? Use that tool!
The same as above but hide the dildo in the bed.
- Where is the pizza?
Hide Lily's pizza during the arrival.
- If you yell, your sister will come
Dance with Lily and follow her.
- Naked at the park
Give the Twins their drinks and make sure they did not leave the party (by having sex with Bill). After the party choose to leave the party with them.
- Look what I've found!
Make sure Karly and Christy had their drinks. Hide the dildo behind the couch in the study or have it on you. Talk to Karly and Christy after the dancing event (you did not need to have danced with them if I remember correctly). Ask them to have sex.
- I am the Black Panther!
Give Seth and Vicky their drink. Get rid of Charlotte and Chanise in the bedroom. Before dancing talk to Seth and Vicky, listen. Follow them to the bedroom and interrupt them. Go to Vicky outside and talk to her.
- Everybody is left?
i have unlocked this but I don't remember what you have to do. I'll try some things.
-Mimi?!
This is the Mimi part of the "nothing better than home" achievement.
- I am not your father!
I have not yet unlocked this one.