Identify relationship building dialog?

Solution 1:

Here is a guide for dialogue choices in FE3H. I would warn you not to scroll too far down and follow the guide as you need it since there are potential spoilers in the guide.

https://www.rpgsite.net/feature/8759-fire-emblem-three-houses-dialogue-choices-consequences-and-support-guide-walkthrough

As a side note, you will usually gain enough relationship points through battle, gifts, and tea time/birthday gifts. I would also recommend starting on hard mode since you can always scale down the difficulty. If you have played other FE games, hard mode should not be very hard for you especially with divine pulse making the game substantially easier.

To directly answer your question, no there is no way to tell in the game what dialogue choices have an impact on your relationship with characters from my experience. I have gotten some by chance and you generally do not need them. For reference I am on chapter 16 of the Golden Deer route. Relationship points may be more important for other routes.