This year's all Game Developers Conference Austin got underway yesterday, with a new lineup of iPhone focused events taking top billing on the opening day.

Brian Greenstone of iPhone developer Pangea Software took to the podium to offer advice on the increasingly difficult task of marketing new iPhone games.

It's a well-known that getting into the top 100 list on the App Store is vital to an application's success, but Greenstone also offered some figures that developers can expect as they climb the charts. The top 100 can expect around 1,000 units to shift each day, while the top ten tend to average nearer 6,000 copies.

"Some of the number one Apps were over 20-30,000 a day," Gamasutra quotes Greenstone as saying. "...[But] your sales drop off rather quickly after they fall off that list."

He went on to explain a few quirks of the App Store that can help, such as release batches of games being sorted alphabetically, and the benefits of fast, hard sales rather than steady, protracted ones in terms of App Store ranking.

Getting the media involved, diversifying developments and keeping costs down also sound like obvious points to make, but Greenstone offered plenty of sound advice to back up his selection of iPhone marketing tips.