With over two million paid downloads for its game Pocket God, Bolt Creative's Dave Castelnuovo should know plenty about how to maximise sales on the App Store.

"We started out focusing on the grassroots community," Castelnuovo explained. "However when that started to drop of, we decided to do some direct marketing."

Splitting the cost with fellow iPhone developer Lima Sky (Doodle Jump), Castelnuovo spent $25,000 (the minimum for the particular slot he wanted) advertising on Gizmodo.

This was targeted over the Christmas session, with the advert boosting Pocket God from #28 to #11 in the US paid App Store; something Castelnuovo said more than repaid the investment at this high volume sales period.

In-app purchase dilemma

In opening up the session to the floor however, it seems many developers remain uncertain about many of the new business models, including freemium games. Even in-app purchases face resistance among gamers.

Lazy 8's Rob Jagnow spoke about his experience with Cogs. It sold at 99c for the first 10 levels, and then each of the four 10-levels packs were available at 99c a shot.

"What we found was that half our audience said they prefered in-app purchases and while half prefered an upfront cost of $5," Jagnow said. "The latter were worried about issues such as a losing the purchases if they changed devices or wiped their iPhone."

Perhaps more worrying however were the 17 percent of people who said $5 was always too much for an iPhone game.

"This was despite us pointing out that the original Cogs game cost $10 on the PC," he said. "Just because the iPhone is a smaller device, they seem to think the games should cost less."