For those grinding affinity for the campers, take note: All the questions you can ask them will raise their affinity by 2 points, EXCEPT for asking them who they think the hottest camper is. Taking girls to the Hot Tub will raise their affinity by 3, and it will also advance time. If you're going to take a girl to the Hot Tub, make sure that's the last thing you do before time advances. Each time slot in the day allows you 4 interactions before it advances, which include interacting with campers by asking them questions, completing different parts of roaming quests like Izzy's panty hunt (Getting the panties and giving them to Izzy I believe use up 1 interaction each), and so on. I know it's a mouthful, but hopefully this will help people who are struggling with camper affinity, especially if they're on the chopping block for elimination.
Also, final note: You can also ask the opposing team's girls to join you in the Hot Tub. Just make sure their affinity is 70 or over, and you're golden.