You’ve read all of your free items this month. To register, get added benefits and unlimited access to articles, Become a Member. Already a Member? Sign in. Advertising Age Article Abstract So You've Got a Mobile App -- Now What? Building Audiences Is Tough in a Crowded Marketplace. Here Are Some Tips By Rita Chang, Published on September 14, 2009 4 Want more Access, Content & Connections? Upgrade to Membership. We are glad you are enjoying Advertising Age. To get uninterrupted access and additional benefits, become a member today. Register Now Already a member? Log in.