Talk to Justin each night and when you see him in the nightmare on landings. He's the guy with the glasses sitting at the left edge of the bar (under the TV). He will be there on:
Day 2 from opening to 21:55. You have a while to catch him here, but once Todd and Archie leave he's next. Answer: "Maybe..."
Day 3 from opening to 22:25, right when Catherine shows up. You have plenty of time here, but you also have a *lot* of people you need to talk to this night if you're going for everyone. I recommend talking to Todd/Archie immediately after they come in, then Justin immediately after that. A: "Men, of course."
Day 4 from 20:25 to 21:30. Talk to him after you talk to Morgan and the Couple. No question.
Day 5 from 20:40 to 22:10. You have most of the night, but once you see Daniel/Anna leave, he's next. A: "It's not your fault."
Day 6 from 20:10 to 21:25. Only two important people to talk to tonight, him and Anna. Plenty of time here. A: "Is there a reason?"
Day 8 the whole night. You can't miss this one, as you are allowed to linger as long as you desire.
You also need to talk to him each time you see him on the landing during the nightmares. He is the "Sheep with Glasses". Just be encouraging here; the answers should be obvious. But let me know if there's one you aren't sure about.
NOTE: I am 99% certain I gave a "wrong" answer or two at the Stray Sheep, according to the wiki, and still popped all the helper achievements. I include the answers so that you can be on the safe side, but you may very well be able to answer however you like. If you have confirmation of this, please comment. If you want to be safe, answer as posted above.