being an introverted guy myself, here is my advice; I say let him know, and make it obvious that you like him and want to be more than friends!
It's completely fine to fall for best guy friend. In-fact most of the relationships were best friends earlier.
A close guy friend can fall in love with a close lady friend. It has happened to a couple of my friends and it can happen if you're close enough to this person.
Get to Know him, and make him fall for you. Remember that old saying, all is fair in love and war. That means tell your friend you like this guy or tell the guy your friend isn't interested! Once you get to know him, he will easily fall for you, happened to me, and I got the guy.
An introverted guy can find a girlfriend in the same types of places as an extroverted guy. Visit a local club or bar, go to the local coffee shop or if you have any hobbies, join a meetup group for that particular activity.
You can try telling his/her parents.
If you wait...he will like you back...
A little bit time after he will fall in love with his best friend... ( well... that happened to me) :)
Be his friend, wait, and don't be intrusive.
If a guy waves at you, he probably wants to meet you/ be your friend. If he already knows you, he's saying hi.
If the guy already likes your best friend, there's pretty much nothing you can do without making yourself look vindictive and manipulative.
act like a good friend and he might fall for you
yes this is typical...