Strategy 1: Persistence
Write a large quantity of quality games. The games must be high quality for this to work. Each game will help you build your reputation. Even if the first game only gets 10 downloads a week, over a year that's over 3000 downloads. Using that platform, you can start putting in-game adds for your next game. When your next game launches, it will already have an audience of 3000 to give it a kick start. By the time you've written 5 games, you will be generating a decent revenue. As you make a name for yourself, websites will start to review your Apps giving you more publicity. It's slow going, but you stand a very good of succeeding in the long run. Angry Birds wasn't Rovio's first game. It was something like their 15th. Imagine how much more momentum they had on launch day with 15 games in the bank!
Strategy 2: Free games
It's pretty obvious that publicity improves sales. Each person who sees your App has a certain probably of buying it. If the probably it 10%, then ten people have to view your app for each sale. With the persistence strategy we're increasing the publicity our games receive over time. Essentially we're cultivating an every growing pool of people who will view the app. Thus, each subsequent app will sell more copies.
With the free game strategy, we're doing something different. We're increasing the probably that each view will result in a sale. By making the App free we're re-balancing the value proposition. The question "Does the values presented by this app appear to be more than $0.99 of my money?" is very different to the question "Does the values presented by this app appear to be more than none my money?" Obviously, the second question will generate more positive answers.
Giving away a free App will give you market penetration. It also has another advantage. There is a chance that a person who's bought your App will recommend it to a friend. Recommendations are valuable because someone is much more likely to buy a product which as been recommended by someone they trust. If 25% of buyers recommend your app to a friend, and all the friends buy your app; if you only sell 100 copies a year you're only benefiting from about 25 of these bonus sales. If you sell 1000 copies every day you'll benefit from 250 bonus sales every day!