Smashing Magazine has a terrific guide to designing “call to action buttons.” Design and optimization can increase conversions dramatically – just ask (and study!) these conversion-focused leaders:

- Social gaming: RockYou, Slide, Zynga, etc
- Flash Sales: Gilt Group, Rue La La
- Couponing: Groupon, LivingSocial

Smashing Magazine lists dozens of examples. I boil it down to the following:

- size and location: think of visiting a grocery store and what catches your eye in the aisle
- color and ‘clickability’: does the button stand out? does it change on hover?
- call to action and copy: what are you asking users to do? is it tempting? This dictates size and location…

With so many variables, the only way to optimize is thorough A/B testing. Cycle through messaging, placement, size… collect data and optimize upon that.

Looking for inspiration? Visit the companies listed above: they are industry leaders in funnel and conversion optimization. Here are two examples from LivingSocial & Groupon. Notice how each call to action has large & colorful buttons, clear messaging and conveys urgency:

Popularity: 2% [?]