From week 4 on the very first thing you must do (except for 2 weeks where you have the chance to choose a new leader first) is to select a unit member for the morning greeting. The idol will then say something and you get 2 possible answers. The sentences the idols say are different for each idol, but the possible answers are the same. Choosing the correct answer increases the intimacy score.
There are two types of idol comments. In the first case of the first type they say something nice, in the second case they complain about something. Even if you don't understand Japanese, it's usually easy to tell the two types apart just from the tone in their voice and from their movements.
In case of a nice comment all your idols will be happy if you answer correctly, on the other hand they will all be sad or angry if you answer incorrectly.
If the idol complains you can either reprehend her, which makes her sad or angry, but pleases the other two, or you can agree to what she said and make her happy, but this will have negative effects on the others. You should always choose to reprehend the idol.