I've just been speaking to a new client about her existing AdWords account and she gave me access to have a look at it for her, as it clearly wasn't working for her.
As soon as I'd opened the account in my Client Centre, it was like an early Halloween! Pretty much everything that had been done in the account was wrong! The horror!
Wrong basic account settings, all broad match keywords with no relevance to the industry, one basic advert covering all adgroups (which included a September only offer!), no negative keywords, no extensions, no, no, no!
It was the exact reason that some people say that AdWords doesn't work. Of course it won't if the set up really is that poor!
The really sad thing was that it had been set up by a major digital marketing company, who, looking at this, have clearly have not been trained in AdWords, or are not bothered about their customers, or both!