So you’ve just developed the most amazing iOS game of all time. Good for you. Now you need to promote it.

Yes, you could spend marketing dollars on advertising. You could build a fantastic website and buy Google AdWords to push traffic there. You could spam every game review online magazine with your carefully-crafted press release. You could create a Facebook page and inundate your friends and family with links to it. But all of those paths rely primarily on crossed fingers and hope.

If your new game is really fun to play, there are five features you can implement directly in your app to nudge it towards becoming a viral hit. The best promotion is word-of-mouth, and if you build your app the right way its users will become your best evangelists.

1. Allow — But Don’t Force! — Facebook Connect

If you believe the six o’clock news, every single man, woman, and child on the planet has a Facebook account. (My friend’s dog has a Facebook account!) Facebook has certainly replaced the local coffee shop bulletin board — and maybe even the refrigerator — as the best place to learn about what is happening in your circle of friends and family. Allowing your users to publish their love of your game to their Facebook wall is an incredibly inexpensive way to spread the word.

You should be considerate, though, and not require users to authenticate with Facebook in order to play your game. Many people are wary of sharing their Facebook credentials with an app before learning exactly what it does and what it might publish to their walls. And, of course, some people simply don’t have Facebook accounts. Let them play your game and give them the option to connect with Facebook. If it’s really fun, and if you make it simple to discover how to connect to Facebook from within the app, they will.

2. Tweet Scores

Twitter is only slightly less popular than Facebook these days. The fact that Apple decided to bake Twitter integration right into the latest version of their mobile platform should be evidence enough of that. If you let your game’s users Tweet their high scores and / or achievements — but don’t harangue them about it — some percentage of them are going to do so. Let them add a hashtag, or a link to your app’s iTunes page, or your app’s website. Many of the most popular iOS games — including Canabalt, Flight Control, and Angry Birds — utilized Twitter word-of-mouth marketing to great success.

3. Challenge A Friend

Even if your app is single player only, allowing your customers to brag and challenge their friends to beat their scores directly from within it is a good move. An avid player may be too shy to post a link to your game on her Facebook wall, but not too shy to challenge her mom to beat her score. The simplest and most intuitive way to provide a “challenge a friend” feature is to let the user choose from her Facebook or Twitter friends, which is why connecting your app to those services are the first two points on this list.

4. Location-Based Leaderboards

Several iOS apps — including QRank and the wildly popular Flight Control — include leaderboards listing high scores of other players based on their relative location to the device. Why do they do this when it’s highly unlikely that a player is going to actually know any of the random users playing their game in the same city or state? They do this because players want to see themselves near the top of leaderboards, and it’s much simpler to achieve success in a smaller pool. If your app has even just a few hundred players it will quickly become exponentially more difficult to rank in the top ten out of all of them. It is, however, possible to vault into the top ten of your home town, or the nearest city. The positive reinforcement of seeing his own name at the top of the Anytown, USA leaderboards can be just the incentive he needs to keep playing, or, more importantly, to convince his friend to start playing.

5. Unicode Distribution

Distributing your game as a single version playable on the iPad, iPod touch, and iPhone is a great way to keep it in front of your users at all times. The additional revenue potentially gained by forcing users to buy multiple copies for each of their devices won’t outweigh the negative feedback.

Epilogue:

There is no way to guarantee that an app will “go viral”, but including these five key features will at least give it the *potential* to become a viral hit.