Hello, this is kinda my second guide any pointers please let me know. So lets get down to business
Im still getting used to how you make the guides all pretty and stuff so bare with me =]

Quinn and Valor were introduced into LoL March 1, 2013. I have tried the champion although I am not perfect with her she is a lot of fun, actually one of the most fun champions i have played with other than Diana. From what I can tell Quinn is an Agressive yet conservative Champion who has decent abilities.

Like all ADC you should go for as much AD as you can get so you should consider AD Marks and AD Quints, while bringing up your Mana Regen with your Seals and your Magic Penetration with your Glyphs.

I think a 21/9/0 Tree is the way to go, the Offensive tree gives you the extra AD and Attack speed boost while the Defensive tree provides you with some extra health, armor, and magic resistance.

While attacking I think this would be the best way to go
Q to Blind
By then Valor should have marked the Champ and you should have gotten some extra hits.
E to slow down enemy champ and also remark
then W for the extra boost of attack speed, also some map awareness which you can benefit from.
And if the champion is low on health and alone you can pursue with your R since it gives you an extra speed boost and when cancelled an area attack.

For spells I Highly suggest Flash and ignite,
Flash is great to catch up with enemy champions but also great to run away.

Easiest way to farm with Quinn is to hit the marked targets, Valor will mark minions with the lowest health, and the extra damage bonus will surely finish them off in one hit.