how do i know if a boy likes me?

It’s not always easy to tell through text, but there are little signs that can give you a clue. If a boy likes you, he’ll usually make an effort to keep the conversation going—asking questions about your day, remembering small details you’ve shared, or replying quickly and warmly. He might use playful or sweet language, send emojis that show affection, or check in just to see how you’re doing.
That said, everyone texts differently, so don’t stress if he’s not super expressive over messages. The most important thing is whether he makes you feel valued and cared for, both in texts and in person. If you’re unsure, it’s okay to take your time and notice how consistent his effort feels.

You can't know, many say that there are some action boy or girl do with people they like, but every person it's different, or can be just kind action.
There isn't a rule to tell it, just feel the heart, and most important, you like him/her?

When he texts you, does he ask you actual questions? Does he try to keep the conversation going even if your answers are perfunctory? Does he try to be funny, or at least amusing?

Or does he write things like, "I really like you"?

Honestly, there are a lot of possible clues.

He will talk about cheese and chocolate with you
call you kind
call you friend
find you funny
tell you he will later return
be nice to you
ask to continue messaging you and play in forum
send many many many gifts
email

exchanging texts is usually a good first sign

Did he dip your pigtails into his ink well?