Please bear in mind that I'm not the author (
HoneyGames is responsible for this great game with helpers) and don't actively help with it. I've spotted a few things and errors at times and tried at least 4 pages of potential paths so I thought I'd give my insight.
People here have asked about a walkthrough on a number of occasions and it's been pointed out that it's nigh impossible given the complexity & number of inter-related story arc. Look around and you'll find a number of posts suggesting which girls you can target as girlfriends, which are just interested in sex and which are currently not really targets.
Best I can offer on the ladies of NCC (feel free to correct):
If you don't want to take a chance and really want to get an idea of which answers give you to best points for the girl you're interested then I suggest you look the individual day files (like "02 day 01.rpy"), character files (like "s 09 rebeccachat.rpy") and event files (like "E sportaward.rpy"). You'll gain some insight into how games like this are written and learn a bit about Python (and RenPy) at the same time.