Here's the formula: Take an attractive girl or woman and make her more approachable by adding in some klutziness.
Like many other klutz characters, a Cute Clumsy Girl's clumsiness rarely does her serious harm but can often set off Rube Goldberg-like chain reactions of disasters. She's never seriously injured, though, and she always pops back up with a good-natured, but rueful, smile. It is almost inevitable that at some point her clumsiness will result in a Crash into Hello.
Occasionally, the klutziness pseudo-flaw is used for a male character, but only rarely, as it is not seen as quite as endearing in males. A clumsy male character will more often be used for straight-up Slapstick (and usually will get hurt), perhaps because of a Double Standard relating to Amusing Injuries.
See also: The Klutz (the supertrope) and the fanspeak page Dojikko (for an examination of this character in anime-specific subculture). If the klutziness tends to take care of her enemies without her even realizing it, she is also The Fool. Compare Cuteness Equals Forgiveness.