Warner Bros. has started casting the role of Luna Lovegood for the next Harry Potter movie, according to CBBC Newsround.
David Yates is set to direct Harry Potter and the Order of the Phoenix, which is targeted for a June, 2007 release.

The talent agents are currently visiting schools across the UK to try and cast the role of the strange fourth year Ravenclaw student, according to ComingSoon.net

Those interested can check the official website of the company and request the casting department members to pay a visit to their school. However, that casting of the character is open only to girls who live in the UK.

The movie tells the story of Harry's fifth year at Hogwarts, where the 15-year-old wizard returns to confront slanderous gossip, a cruel new professor and a Ravenclaw girl, Luna Lovegood, on whom he has a crush. Harry visits the family home of Sirius Black, where he learns about the mysterious Order of the Phoenix.
Amid disturbing dreams, unraveling a dire prophecy, and studying for the Ordinary Wizarding Levels exams, Harry and his friends struggle into young adulthood.

Luna Lovegood

Ravenclaw, Y12 - Y19.
Hair: dirty blonde, waist-length and straggly.
Eyes: protuberant, with very faint eyebrows.
Distinguishing features: dreamy look, often seems to have turned up wherever she is completely by accident .
Interests: holds a variety of rather strange beliefs which seem to have no basis in fact, but her steadfast faith and calm demeanor are in some ways her finest strengths. While she believe in Crumple-Horned Snorkacks, she also believes that she will see her deceased mother again after death, and it is this belief which comforts Harry
House: Ravenclaw, same year as Ginny Weasley.

Name derivations
"loony" Eng. slang - 'crazy,' from "lunatic", which is from luna = Latin, 'moon', derived from the belief that sanity is affected by the phase of the moon.
"love" + "good" could refer to the fact that Luna shows the rather peculiar but admirable quality of loving those who don't show much affection toward her (judging by the way she acts towards those she knows are ridiculing her and stealing her things).

"Wit beyond measure is man's greatest treasure..."
- Luna Lovegood, unexpectedly

"You can laugh, but people used to believe there were no such things as the Blibbering Humdinger or the Crumple-Horned Snorkack!"
- Luna Lovegood

"I think I'll just go down and have some pudding and wait for it all to turn up - it always does in the end -"
- Luna Lovegood