Overwhelmed by everything you can A/B-test in marketing? Here's a look at the most critical areas to focus on first.

One area is design, which includes image size, form length, and video. For example, A/B-test various sizes of the same image, recommends Formstack in the following infographic.

Another area of focus is messaging, such as the headline, call-to-action button, and voice.

"Tinker with your submit button to increase clicks," recommends Formstack. "Simply adding one word after 'submit' can increase conversions up to 320%."

To find out more about what critical elements to A/B test, click or tap on the following infographic: