how can i show the guy that i like him?

if u think he dont have any other gf or love and he loves you. then go to him and ask whom he loves. if he says no one, say him that what if i love you.

If u r realy in love with a guy u need not to do anything because he will automatically come to feel the warmth of ur love. But if u r desperate to make him know verbally then go ahead and make use of world love day I mean Valentine's day and open up ur heart in front of him. Sorry can't help you more than this because i beleive that everyone has his/her own unique way of proposing depending on the situation. Everyone one has his own Love story. U have to choose ur path urself. Best of LUck!!!