Quiet girls are cutest!
In most series there is always that one girl: meek, aloof, emotionless, sickly, or hiding in the library. Usually a huge contrast to that loud active character. It might take some time for them to warm up to you, but when they do they are the sweetest (or craziest, but that is okay too).
"A kuudere is like snow: it may be cold and harsh at first glance but it is also what keeps autumn's seeds warm and safe until spring."
A dandere character is one who is normally quiet and silent, possibly to the point of coming across as an Emotionless Girl at times, but will suddenly become talkative and sweet and cute when alone with the right person if they manage to push the right button to get them to pour their heart out, revealing that she (or he, of course) is actually just shy.
The name comes from an abbreviation of 'danmari deredere'. 'Danmari' means to be calm or to shut one's mouth up all the time, while 'deredere' means lovestruck.
The enigmatic emotionless character. Sometimes the anchor in the midst of chaos; other times just quietly mysterious. Draws attention to herself simply by her non-reaction. Can be seen as purposeful, cool in a crisis, i.e., "she's all business."
Painfully shy and quiet, the Shrinking Violet is the withdrawn character, usually but not always female, who walks through the school hallways with her head down and wants nothing more than to blend in with the scenery to avoid all attention because she believes that her presence is worthless or unwanted.