mr. Pokemon
If you take the red gyarados scale to Mr. Pokemon (The guy who gave you the egg at the beginning of the game), he will trade it for the experience share.
you ask him if he likes you
Find a nice hobby to refocus your attentions.
You ask him
You should just come out and ask him if he likes you.
Have someone else do it for you.
Ask a friend to ask that guy if he likes you.
If that guy talks to you more then he does to other girls.
ask him if he likes another girl and if he hesitates and looks at you weird he likes you
In Pokémon HeartGold, there's a guy in Ilex Forest who will give you HM01 Cut after you find his 2 Farfetch'd who are hiding in the Forest.
find someone else to like
it can mean that he likes you