We know that Jo's given us fantastic, strong and fascinating characters that we like to borrow and create our stories with. What you may not know, is that the main characters fall pretty much in line with the personality traits traditional to their star sign. I know one author in particular has used this to get a handle on Charlie Weasley and I think it's a useful, fun way to keep good characterisation in our FanFictions. Feel free to add your own!
Harry Potter - Leo
Generous and warmhearted
Creative and enthusiastic
Broad-minded and expansive
Faithful and loving
Pompous and patronizing
Bossy and interfering
Dogmatic and intolerant
Ron Weasley - Pisces
Imaginative and sensitive
Compassionate and kind
Selfless and unworldly
Intuitive and sympathetic
Escapist and idealistic
Secretive and vague
Weak-willed and easily led
Hermione Granger - Virgo
Modest and shy
Meticulous and reliable
Practical and diligent
Intelligent and analytical
Fussy and a worrier
Overcritical and harsh
Perfectionist and conservative
Ginny Weasley - Leo (Look up!)