I wouldn't start with a pick up line. That's incredibly cheesy.
Most people start with a mutually beneficial, environmentally sound, or conventional opener. Asking about the weather is dull and uninteresting, but it was a standard way of opening up a conversation. If you're both students, you can ask about timetable, teacher, homework, something that happened in class. If you noticed that he is wearing something unusual, compliment on it.
It does not need to be flashy. It does not need to be impressive. It does need to feel normal, it needs to be comfortable, and it needs to develop into a conversation (casual one at least). If it sparks up a minor chuckle, it's fine so long it's not an insult to you or him. A casual hi is better than nothing. Be down to earth enough that you can laugh at your own mistakes; it shows that you're human.
Surely you have made friends before. If you think back on those times when you first met, you warmed people up before it developed into anything, irrespective of whether they became friends or not.
I can't speak for other people, but being able to be intimate, having fun, engage in a conversation, and showing the appropriate level of interest, are better than having the prettiest face in school when it comes to dating for this straught guy. A person who is human (who connects, is personable, is down to earth) is far more attractive in my book.