The best guide will be the forums like these itself. then if you want specific ebooks, I would suggest Adwords for dummies
Agree with the above post. Also nothing will beat experience with trial and error. I would google for adwords tips and read through the top few, i think you'll find similarities between which you can utilize. Also recommend downloading the Adwords Editor program, much faster and efficient than creating and editing via web.
I personally don't know of a free adwords guide I can mention, but Beating Adwords is the best guide I have read about learning google adwords. It's an ebook that explains step by step how to set up a profitable adwords campaign, they talk about how to achieve high CTR and the importance of Quality Score. And what I learned is that the same methods taught in this book could be used on the other PPC engines such as Yahoo and MSN. Anyway, that's my .02c!
there are many on the Internet,digitalpoint also has a lot of!suggest look more experience, then in operation!
Perry Marshalls Definitive guide to Adwords Beating Adwords by the Wealthy Affiliate Folks and Double Digit CTR by James Schramko If you start at the top and work your way down that list you will be a PPC Ninja....
Beating Adwords is quite good. You can get all basic information there. Then you can try by yourself.
Enough information is given in adsense help centre and there is no other guide to beat the step by step instructions given in google. And the other source is DP forums " An Ocean of information "