Pay-per-click (PPC) advertising will only be worth your while if you stay agile with your campaigns.
Here’s a few things to keep top of mind:

Negative keywords – A negative keyword is a special kind of keyword matching option that allows you to prevent your ad from appearing when the specific terms are a part of the user’s search. If your goal is to find qualified leads, negative keywords will help filter out some of the traffic that you may not want.

Conversion tracking– A conversion is an action that a customer takes on your website that has value to your business, such as a purchase, a sign-up, or a view of a key page. These actions are called conversions because a customer’s click translated — or converted — to business. Think of it as the cha-ching! from your cash register. Conversion tracking answers the question of how many views or clicks result in an actual purchase, sign-up/registration, lead, viewing of a key page, or some other valuable actions.

Geo-targeting – it means having the ability to target a marketing or advertising campaign at a limited set of visitors based on their physical location. Advertising programs that support geo-targeting allow you to control where your ads are displayed based on parameters like country, province, city, or even within X kilometres of a postal address. If you want to drive foot traffic to your brick & mortar store, you can limit your campaign to only be shown to people who are within 40 kilometres of your shop using geo-targeting.

Ad extensions – Give potential customers more reasons to click on your ad by including additional business information upfront such as your address and phone number, more website page links, or product information. This extra information, called ad extensions, will appear with your ad on Google.com. In the world of search engine marketing (SEM), you have to juggle many methods to make sure a PPC account is running efficiently. Throwing Ad Extensions into that mix will add an extra edge to any PPC account. When all else is equal structurally, Ad Extensions are SEM’s “X Factor” and can differentiate the top performers from the mediocre.

Some key findings about the average campaign relating to the above (done by Wordstream’s Grader)

• Very low number of keywords or negative keywords added in the last 90 days.
• Very low number of ad groups and ad text added/edited or deleted in the last 90 days.
• Very low number of campaigns added/edited or deleted in the last 90 days.

Most advertisers aren’t really taking advantage of even the most basic Adwords account optimization tools, like conversion tracking, geo-targeting, or ad extensions.

Furthermore:

• More than 50 percent of them don’t even check their accounts once per month.
• Almost 25 percent haven’t done anything to their account in the last 90 days.
• More than 20 percent of them have yet to use a negative keyword and less than 50 percent have used at least one negative keyword in the last 90 days.

Sources: Google About.com Search Engine Watch Google Blogspot ClickZ