There's plenty of information out there about what A/B split testing is, but the ultimate success of your testing will be largely determined by what you test. So, how do you know where to start with your testing?

First, identify which pages of your website you will test. Choose pages that have a specific focus or single goal for users–these will be much easier to test than your home page or other pages that have multiple paths of action. Next, decide on which page elements to test. Examples of page elements are: headings, introductory copy, graphics and photos, main copy and testimonials. Start with elements that appear "above the fold" or near the top of the page, and place extra focus on promotional and limited time messages.

By knowing what to test, you'll be able to design more effective A/B split tests, ultimately improving your click-throughs and sales.