Paul Boutin wrote in “11 things I didn’t know about app development”,

Most app discovery comes from viral word of mouth among customers, not from people searching app stores for something to download.

I don’t know what it’s so much of a revelation to developers. The App Store is a warehouse of digital goods, a distribution platform, a vending machine.

Of course it’s a crowded place but how is it different from the web? or the desktop application market? Do you seriously still believe you just have to put a website online and the audience will come like magic?

No, you have to find a way to attract users; why the App Store should be a different place?

I think the single mistake Apple did when it introduced the App Store was to say to developers: “focus on building apps and we’ll do the rest (hosting, distribution, payment and marketing).”

Actually what Apple truly meant by marketing was: we will feature your app but only if it brings value to users and if it matches our design expectations.

So, put it simply, it’s your job as a developer to (1) build an app people would want; (2) build an app Apple would want to feature; (3) do the right marketing campaign and word of mouth to bring the application in the top 100.

Nothing else matters.