You don't need any guide its a waste of time.
Every time you get a heart you did something right in a dialogue with a girl. If you didn't get a heart pulsating in the top corner of the screen just go backwards. Or go to a save before you picked one of the dialog options. Rinse and repeat you are now on every single girls path.
The game introduces this when you first install the game. If you didn't skip you would know this. This is a basic element that every single dating / jrpg / novel dating game like this has.