Ernesto, I hired a consultant to improve our existing Adwords campaign. Between organic and paid search (Adwords, etc.), a ton of people are finding us online.
At the beginning of the year, I hired Adam Kreitman (wordsthatclick.com). He is an Adwords consultant. He asked me what I wanted to accomplish. I told him I wanted to decrease costs 10%, increase number of clicks 10%, and increase the quality of client by 10%. This guy is amazing, because he has decreased costs by 40%, increased quality of clicks by a good 30%. We are a little short on increasing clicks, but . . . that's primarily because we have eliminated SO many bad clicks, it's hard to make up for all of them.
If you haven't had someone optimize your Adwords campaign, it's worth doing.
Here's an example: I want people who are interested in carpet, but not car carpet, truck carpet, etc. We are no longer paying for clicks for people looking for carpet for their Audi. It makes a big difference.