Ginny Weasley: A Description
As the youngest of the Weasley clan, not to mention the fact that she's the only girl, Ginny Weasley tends to show traits that the boys don't. The older boys (Percy aside) are known for being jokers, Ron is a stubborn but loyal friend and has yet to cause any great upset at Hogwarts and Percy is simply the black sheep of the family yet even he posesses the trademark Weasley stubbornness.
Though it would be wrong to say Ginny is nothing like her brothers, she is still not a mini-Molly or a female Ron and it's necessary to remember that when writing her; particularly in relationship fic.
Ginny Weasley has her head screwed on. She may have seemed young when we first met her (lusting after Harry in The Philosopher's Stone) but by the time we reach OotP, Ginny has matured a great deal and shows just as much common sense as Hermione, perhaps more so since despite her unfortunate past in the Chamber of Secrets, she seems to have managed to keep her head down to the extent that even Harry has forgotten who knows the most about being possessed by Voldemort.
"We wanted to talk to you, Harry," said Ginny, "but as you've been hiding ever since we got back -"
"I didn't want anyone to talk to me," said Harry, who was feeling more and more nettled.
"Well, that was a bit stupid of you," said Ginny angrily, "seeing as you don't know anyone but me who's been possessed by You-Know-Who, and I can tell you how it feels."
However, just because Harry has forgotten, doesn't mean Ginny has, as is made clear when she responds 'lucky you' to Harry's admitted memory lapse. Ginny seems to break through Harry's 'woe is me' attitude enough to actually make him feel better, something that neither Ron nor Hermione have managed to do. She may not me one of 'The Three' but she is certainly a valued friend not only to Harry and the other two but also to Luna and Neville.
Having accepted an invitation from Neville to go to the Yule Ball with him (GoF), Ginny does not seem particularly bothered to have to turn Harry (via Ron) down when Harry has no one else to go with. Similarly, Ginny is happy to sit by Luna and tells the others that 'she's not that bad' when a number of students will quite happily hide Luna's things just because they think she's odd. Hermione, too, values Ginny's friendship and in GoF correctly entrusts her with the secret that Viktor Krum is her partner for the Yule Ball.
That being so, the new mature Ginny still knows how to have fun and she's certainly not averse to winding Ron up when the opportunity presents itself, for example, by dating Dean Thomas (after a year of seeing Michael Corner). Unlike Hermione, when Ginny watches her brother's battling tables in GoF, she is not torn between what they should be doing and what they are doing but instead laughs along with Fred and George.
In OotP, Ginny reveals herself to be an adept liar, a skill which she can only have got from the twins since Ron's face tends to match his hair whenever he is untruthful. She's also happy to conspire (as is Luna) to aid Harry in breaking into Umbridge's office to use the fireplace and remains cool and calm throughout this fairly risky period.
Ginny reveals herself to be very talented in her classes with DA but is hindered by a broken ankle when she most needs to use these skills. She does not, however, wimp out and is keen to carry on despite her obvious pain. It is with reluctance that she allows Luna to assist her in walking, preferring to try to manage herself.
All in all, Ginny has an experience beyond her years (as have many of the character's in DA but even more so thanks to Tom Riddle's diary) and a maturity to match it. She is loyal and open to friendships with people who are hardly the most popular of students, she is calm and collected in difficult situations (JKR often uses 'Ginny replied cooly' and 'Ginny said calmly' to describe Ginny's manner of speaking) even if she can be a little short tempered at times (particularly with Harry and Ron). The leaps and bounds of character development that have occurred in OotP would suggest that Ginny is likely to play a very major part in the remaining years at Hogwarts but we'll just have to wait and see where JKR wants to take the littlest Weasley.