Clicking the "Online Help" button and translating the page helped me figure out most of them.
For endings 1, 3, and 4, when you get the option of taking her to the party or to the nurse's office, you need to pick the nurse's office.
Ending 1: Either needs low Lewdness or the Play tendency needs to be neutral (I would say less than 30 of either Service or Pleasure would work). You get the "pregnant belly" item as a reward.
Ending 3: High Lewdness and high Pleasure. Doesn't look like you get any reward for this one.
Ending 4: High Lewdness and high Service. You get "Dog Clothes" as a reward.
For endings 5-7, you need to choose to go to the party when given a choice. All of the endings give the "Sexy Dress" as a reward.
Ending 5: Basically, just use the basic "Hypnosis" state a lot.
Ending 6: Use "Paralysis" a lot.
Ending 7: High lewdness.
Ending 2: ...I think this ending is the basic ending after choosing the Party option if you don't fulfill the conditions for Endings 5-7, but I haven't been able to confirm yet.
To get the rewards for the endings, you need to either load or start a New Game+ from the Auto-save.
Now, a note about Lewdness: Dirty Words are basically the big key for controlling it. If you don't want Lewdness to rise, turn off all the Dirty Words. If you want to increase lewdness, forcing her to masturbate during class while under Common Sense Overwrite is a good way.
Play Tendency: To put it simply, if the man climaxes or inflicts pain, Service rises. If the woman climaxes, Pleasure rises (using toys, fingering, anything other than penis generally works fine).
Dependency: Slut causes it to rise a lot, Common Sense Overwrite increases it a little, Paralysis cause it to drop, and Hypnosis keeps it from changing at all.