Free is the new 99c on the App Store, but while there are plenty of websites set up specifically to handle such promotions, some developers are happy to do it themselves.

Released in August 2009, Candycane's Fling! puzzler provides a great example of how to do this.

It went free for five days in September, and since had been updated nine times, as well as gaining support from a Lite version, also released in September.

The result has been 600,000 paid sales and 4.2 million free downloads.

Developer Michael Bevin explains how the process worked.

Pocker Gamer: Discovery is a major issue for iPhone developers, so how have you dealt with this in the case of Fling!?

Michael Bevin: The main thing was simply giving it away for free. Giving away the full version for a few days gave it a big boost, and then when the free trial version was finally approved, it really took off.

By giving away enough content for free, I believe a good game can take-off through word of mouth. Back when we gave away the full version of Fling! for free it wasn't such a common tactic and we were a bit unsure about the whole idea - watching the downloads and thinking that we're losing half a million potential buyers. But it worked out well.

Now this approach seems a lot more common, with sites such as FreeAppADay for example.

How have you promoted the free version of Fling!?

We haven't really done any promotion. I guess the key is ensuring the free version has enough content that it provides a good amount of fun, while still giving users an incentive to buy the full version.

What's the geographical spread of downloads been?

The US and UK are by far biggest markets, perhaps because the game's only been available in English. We'll be releasing some additional language support in an update soon.

How have the majority of your paid sales come about?

There was the big peak shortly after the free version came out. Following that it's been very steady without any price cutting (we're not going below $1) or promotions.

What's the conversion rate in terms of upselling from free to paid versions?

It's close to 10 percent.

How much has paid activity dropped off over time?

After sitting at the top of the App Store for about a month, it slowly dropped off from that peak over a couple of months, but has then been fairly steady over the past four months. We've been very pleasantly surprised how it's sat near the top of the puzzle charts for so long.

We've also been steadily releasing updates with improvements. which help keep sales up - not because we find doing updates gives a significant boost any more, but because a better game is something more people want to buy and tell their friends about.

Hence in many little but important ways, it's a much better game than the one that sat at the top of the App Store for a month.

We've fixed small issues and confusions that we found users were having, made more and better-paced levels, included a global free-play leaderboard, and Facebook integration for viewing friends' high scores. And we plan to continue with such updates for a while.

What's next for CandyCane?
Fling! is being ported to a bunch of other mobile platforms by Player X, and so far has been quite successful on Java and Brew.

We're also planning a follow-up to Fling!, which should hopefully get an initial kick from the success of Fling!

Thanks to Michael for his time,

You can follow Candycane via its website and Twitter.