Your choices in particular dialogues determine which trait gets the point. I save before dialogue encounters with NPCs that I know from the original game will result in a trait choice so I can change my choices to get the point in the trait I want. This also holds true with some dialogues between the main characters. There is a limited number of dialogues for each trait so once they are all done you can't add more points to that trait. You didn't say where in the game you are so it is hard to say if another dialogue will come up that will give you a chance to choose that trait.
