Note that I personally can't reach orgasm together with the student. Might be broken (and considering how many weird things I have with her, I think she is definitely broken.
1st girl:
-Talk to her casually and if the arou sal doesn't increase, flirt with her until it does.
-Eventually, she will begin to strip, and invite you to give you a handjob.
-After that, feel free to do whatver you want.
-You can have er sitted and you going up to see her, have both of you standing, have her standing and you sitting.
2nd girl:
-Almost the same, talk to her casually, she won't be hard to convince since she's an exhibitionist and really want to get it.
-You can give your seat (which unlocks anal), have standing or sitting sex (vaginal, handjob, blowjob)
3rd girl:
-That one is annoying. First step is the same as before, talk to her casually, she will eventualy show her breasts.
-If her arousal is high enough, she may remove her pants.
-And now it gets tricky, she has a lot of free will and is a dom, if she gets annoyed with you, she might initiate sex, and raise attention a lot, and you might be arrested.
Sometimes she tells the other officier to either watch or ignore you, sometimes, you will be caught. If she initiates sex, there is no way to stop her, so try to lower attention before flirting or talking with her when she has high arousal.
-You can have have sitting sex or standing sex, standing sex has both anal and vaginal. Blowjobs are hard to get, and almost a death trap.
-Don't even dare touching her before she touches you, she will stop you and raise attention by a lot.
3somes:
When you get all the trophies, you can get another girl to join in under certain conditions, read the changelog some posts above to know what they are.
Over all, the game is "nice", but very rough around the edges, there was more work put into the first woman than the others, that are ironically behind a paywall (a very low paywall, but still a paywall)
So you'll probably get bored before trying to get all the achievements.