Scott Kveton is the CEO of Urban Airship , a mobile services platform provider. He is an expert on mobile app strategy and cloud infrastructure and speaks frequently on app monetization and engagement, developer ecosystems and cloud computing.

In-app purchasing (or in-app billing) on the Android platform is one of the most attractive ways to monetize a mobile app. Android developers now have access to a source of previously unavailable revenue. They can offer premium features, including unlocked content, paid downloads, upgrades and expansions for games and content packages.

As Android developers start to integrate in-app billing into their mobile offerings, they should know what works and what doesn't. Drawing from my company's experience helping thousands of customers optimize their products with in-app purchase features, I've compiled this list of best practices.

Do make it clear in the description that the downloaded app can be augmented with additional features via in-app purchase. This is an app’s first opportunity to market future add-ons and they should let users know upfront that the app is feature-rich and expandable.

Do make the purchase process super obvious to the user. Users should never feel they purchased something by accident, nor should they be unsure what’s going to happen once they click the purchase button. Plus, refunds are a pain to process and should be avoided at all costs.

Do test different pricing. Try to offer a variety of items at different prices. A user may not want to fork over $20 for a fully featured app, but it's possible that they will pay for a lite version at a reduced price. Don't take the option off the table.

Note: Pricing is one area where iOS and Android differ. Apple prices by "Tiers," with tier 1 starting at $.99. Apple then converts that into the local currency for international markets. Android has no tier system; developers set an arbitrary amount. Android just deployed currency conversion, but not everything is supported. Developers should pay careful attention to Google's guidance on this.

Do evaluate a freemium revenue strategy whereby the app is free with in-app purchasing options. People have unpredictable ideas about how much apps are worth. Some are unwilling to pay even $0.99, but that may change once the user is hooked. Once they are engaged, users are less cautious about spending money on additional features and content. Developers using the freemium model can hedge their bets against subjective valuations of their apps.

Note: In-app purchases can increase the per-user value of a simple app download. Free apps have greater reach and up to 10 times more users than paid apps, by some counts. With greater reach, conversion rates also go up. With that tenfold increase in exposure, a free app has the opportunity to attain the same revenue as paid apps by converting only one-tenth of its user base. Remember, revenue from app downloads can only be collected once per user. In-app purchases allow ongoing revenue from each user.

Do repurpose existing and archived content to leverage the long tail on the mobile channel. Most companies will have some content they can turn into an in-app purchase. A news app, for example, could offer back issues, or even single articles, as in-app purchases. For example, an app for a recording artist could sell live versions of songs or outtakes from a recording session. Many brands have existing content that engaged fans will pay for. The mobile channel offers an easy way to tap into that demand.

Do consider the size of the app. There are two ways to add content to an app after the initial download: unlocking hidden content for users post-download, and offering additional content as in-app downloads. Most apps are limited in size. iOS directs users to a WiFi network for apps over 20MB, whereas Android limits apps to 50MB. Apps that contain hidden content are less dynamic than those with content downloaded later. Because the app already exists in its entirety, the only way to add or change the content is by updating the app. Developers should be aware these additions will increase the complexity of the app.