I've tried to keep the guide as vague as possible so that you'll hopefully be able to use it without having the juiciest bits of the story spoiled for you. That said, this is a guide for getting all the endings and achievements, so if you can't tolerate some minor spoilers then don't read this until you've at least beaten the game once.

Ironically enough, the most spoilery parts are the general hints on how to get each ending, so I've put spoiler tags around those. The rest of it is just one set of choices that would let you get that ending, which I've left outside of spoiler tags because they don't spoil much and they'd be annoying to read with spoiler tags on them.

Exclude Jupiter from the group

1. Venus + Neptune
   
2. Jupiter + anyone
   
3. Neptune + Venus
   
4. Venus + Neptune
   
5. Neptune + Venus
   
6. Jupiter + anyone
   
7. Venus + Neptune

Exclude Venus from the group

1. Venus + anyone
   
2. Jupiter + Neptune
   
3. Neptune + Jupiter
   
4. Jupiter + Neptune
   
5. Neptune + Jupiter
   
6. Jupiter + Neptune
   
7. Venus + anyone

Exclude Neptune from the group

1. Venus + Jupiter
   
2. Jupiter + Venus
   
3. Neptune + anyone
   
4. Venus + Jupiter
   
5. Neptune + anyone
   
6. Jupiter + Venus
   
7. Venus + Jupiter

Don't exclude anyone from the group. Make your choices carefully to avoid favoring anyone!

1. Venus + Jupiter
   
2. Jupiter + Neptune
   
3. Neptune + Venus
   
4. Venus + Neptune + Jupiter
   
5. Neptune + Jupiter
   
6. Jupiter + Venus
   
7. Venus + Neptune

1. Venus + Neptune
   
2. Jupiter + Venus
   
3. Neptune + Jupiter
   
4. Venus + Neptune + Jupiter
   
5. Neptune + Venus
   
6. Jupiter + Neptune
   
7. Venus + Jupiter

The sixth choice you get to make is who will go play "Seven Minutes in Heaven" with Jupiter. If you choose to send Neptune with Jupiter then you'll get the achievement shortly thereafter.
https://www.youtube.com/watch?v=8mGBaXPlri8