Stompernet released a very interesting video containing a series of optimization tips for websites.
The most interesting tip was this pie chart they revealed. It shows the results of study on what is the most important parts of your Google PPC campaign to focus testing on.
In the pie chart above:
The #1 thing to test on your Adwords ads is the Headline
The #2 thing to test is your Offer (Lines 1 and 2 of the ad)
#3 is the Display URL. Surprisingly, this one had little influence.
But the big surprise is this.
The biggest impact on ROI comes from testing the actual Landing Page.
Many advertisers forget this.
You can watch the StomperNet video here.