Confirming the rise of mobile marketing as a medium to reach on-the-go consumers, the Interactive Advertising Bureau recently released its first set of guidelines for advertisers looking to target consumers with mobile apps. The report, entitled Prevailing Mobile In-Application Advertising Formats, evaluated app platforms for popular mobile devices to offer insight on best practices to marketers.

To start, the report shows that 300×50 pixel banners are currently the most effective in terms of size for the average smartphone users. However, authors acknowledge that Apple’s mobile devices have larger screens and may require larger 320×480 ads to avoid potential empty space.

On a similar note, the survey found that iPhones and iPod touches currently support the widest variety of creative sizes, while other popular devices – including BlackBerries and Androids – work better with small banners. Meanwhile, the iPad is in a league of its own when it comes to display ad sizes.

With this in mind, the IAB encourages marketers to avoid repurposing smartphone creative for tablets. It calls this practice a “huge missed opportunity” as it overlooks the rich ad experience available on tablets.

Notaby, the iAd platform is showing substantial ROIs in the initial weeks since its launch, likely because of what Steve Jobs referred to as the iAd’s aim to offer “advertisers the emotion of TV with the interactivity of the web and offers users a new way to explore ads.”

But marketers should remember to cater to the non-Apple mobile users when building mobile app campaigns, as well. According to comScore, mobile app usage has grown across the board this year, increasing 112 percent over 2009.