That old song “You Can’t Roller Skate in a Buffalo Herd” (Roger Miller) comes to mind as I try to increase sales for my app, Tony’s Tips for iPhone Users, through the App Store. As an early developer I thought I could skate downhill, using the App Store’s own momentum as it grew (and pretty much that’s what I’ve done so far). But the roar I’m hearing is 3 billion app downloads in 18 months for more than 125,000 apps.