You can tell at a glance that this boy or girl is not a serious person. Where can it be reflected?

At first glance, I know that this boy or girl is not a serious person, generally from the following aspects:

1, clothes, men and women who are not so serious, often have weird clothes and strange tastes.

2, talk, not so serious feelings between men and women, swearing, rumors.

3, manners, not so serious men and women, often words and deeds are different, what they say, and ultimately can not reach an agreement.