Make him have a harem of girls all vying for his affection, which must include (but doesn't have to be limited to) the following:
- a "tsundere", which basically means a girl who gets angry and loses her temper easily in a comical fashion, usually taking it out on her love interest. However, she also has a hidden soft, romantic side which comes out only around the love interest.
- a "Rei clone", basically a girl who is based heavily on Rei Ayanami from Evangelion. This girl doesn't show any emotion at all, making her seem like an alien or a robot (which sometimes she actually is). However, she warms up to her love interest and eventually starts showing emotion due to his kindness towards her. Bonus points if the girl has short hair in a shade of gray or blue.
- a "Yamato Nadeshiko", which is a woman who is quiet, kind, motherly, good at domestic activities and is obedient and submissive towards her male love interest. She often has long hair in a dark color, most commonly black or brown, and is often seen wearing kimonos.
- a Lolita or "loli", which is a character who is a lot younger than her male love interest. Her personality may overlap with any of the types mentioned above, otherwise she is just a normal, cutesy little girl. Often in school settings, the loli character is academically gifted and skips several grades, which explains why she is in the same grade as the rest of the characters.
Make sure that the girl who you want to end up with the guy is the first one he meets.