~ Greetings
After playing for a while, you will have many chances to meet the girls at school or sometimes when you go out. You can greet her or ask to walk home with her. At first, the girls might say no. But after you get closer to her (try to get events with her and pass her checkpoints), she will start to talk to you more and more. You can check a girl's affection from the face icon on the left screen when you are with her. It starts with neutral face and will change to smiley face when she likes you more.
~ Greetings
Sometimes you will meet the girls during school or when you go out. If there are 4 choices, that means you have to pick your way of greeting her. Most of the time, the first two choices are regular greetings like calling her name or saying "Hi". The third choice is to "chop" which is like hit her lightly on the head or knock her knees. And the last choice is to keep quiet and not calling her at all. (The greeting choices will change as the girl's affection toward you changes.)
If you meet the girl before or after school, you can ask her to walk with you. The first choice is to ask her to go together and the bottom choice is to walk alone. (Better choose the top one if you want to get close to the girl.)
If the girl likes you enough, she may be the one asking to walk with you. You also have 2 choices. The top one is to walk with her and the bottom one is to reject her. (Again, better choose the top one if you want to get close to her.)
~ Misc Events
In some events or some random encounters, you might have to answer some of the girls' questions. I'll cover more about the choices at Misc/Misc Events.