One big indicator that someone is totally into you is by checking to see if that person has reached out to you via social media. This means someone is thinking about you when you are not together and wants to learn more about your personal life. If they send you a text message just to see what you are doing, or texts you all day long, then they probably can't get you off of their mind. Constant communication is a clear sign that they have a crush on you. If someone has a crush on you, they may lightly make fun of you, not to hurt your feelings, but to make you smile. That is a common method of flirtation. Along with teasing, watch for funny conversations. Chances are, they will try to keep conversations light and funny to get you to laugh, if they have a crush on you. It can be hard to tell if someone always tries to look their best, or if it is for you. If you are Facebook friends, try looking at their photos to get a sense of what their appearance is like when you two are not around each other. If it seems that they try to look at their best only around you, then you know they are trying to impress you. If someone stops at a shop you love to buy you a special gift, or surprises you with a little treat, then it is a sign of a crush. They want to make you happy with their small gestures of affection and show you that they care. If someone is always willing to spend time with you and never misses a chance to see you, then you can be sure they have a crush on you. Watch to see if they attend the same parties as you or cancels on other plans to hang out with you. If someone is crushing on you, be ready for compliments about even the smallest changes you make. Someone who likes you will notice when you get a haircut or buy a new pair of shoes, and they will let you know about that new change with a compliment.

TL;DR in Vietnamese:
Cô ấy theo dõi bạn trên mạng xã hội. Những tin nhắn không có nội dung rõ ràng. Cô ấy nhẹ nhàng trêu chọc bạn. Chăm chút ngoại hình. Những món quà đặc biệt. Lượng thời gian mà cô ấy dành cho bạn. Những lời khen.