What makes a successful application? ME sat in on several sessions at this week's BlackBerry Developer Conference where advice was being dispensed on best practices.

They covered everything from development guidelines and distribution through to marketing and customer service. We've tried to sum up some of the key points from sessions hosted by RIM experts, but also independent developers giving their experiences.

While they're focused on BlackBerry, many of these points are more general, and could apply just as well to iPhone, Android and other mobile platforms.

DEVELOPMENT

It's worth considering older BlackBerries. According to Marcus Watkins of Versatile Monkey, nearly 30% of his users are on OS 4.5 or lower, so creating a version for 4.2 meant he could target all the Curve and Pearl users. AP Mobile's Jeffrey Litvack said according to his stats, the 8330 is still the biggest BlackBerry. Meanwhile, RIM's Neil Sainsbury broke down the OS share with figures from May showing that 9% of users were on 4.2.1, 20% on 4.2.2, and 15% on 4.3. “Apps written for 4.2.1 can hit around 97% of the audience,” he explained, while also saying that in May, the older Curve had 45% of the BlackBerry apps market.

But also target the new ones like the Storm 2. Sainsbury pointed to the PR benefits of being first to support a new handset in your app's genre, and highlighted the ability for new press coverage too, when you release a new version taking advantage of a new device's features. “You can piggyback on the buzz around those devices,” he said.

Style is important. “There's no amount of technical knowledge behind the scenes that overcomes that 'it slides when it comes on the screen' thing,” said Watkins. And if you're a coder rather than a designer, you can get some useful tips from the BlackBerry App World client itself.

Don't over-complicate things. “Just because you can put certain design elements or features in, doesn't mean you should,” said Jeffrey Litvack of the Associated Press. “Just because I can shake the iPhone, doesn't mean I want to shake it with a news app! Try to discourage your clients from doing things that are plain silly.” He also advised caution when working with a list of features you'd like to add, suggesting that a wise policy is always to hold five back for the next version.

Don't skimp on testing before you launch. Litvack pointed out that just testing your app in emulators isn't enough. “Don't trust that! You have to live with the device, and live with the experience. That's how you test it best.” Sainsbury recommended services like Device Anywhere that let you remotely test on a range of real devices, but also advised using forums to recruit beta testers, giving them a free copy of your app at the end to say thanks.

Automatically check for updates. On BlackBerry App World, this is automatic, which may lead developers to think they don't need to include the feature. However, if your app is being distributed elsewhere, it'll be up to users to upgrade. But do the job for them. “If you have a button saying 'check for updates', I can guarantee it will not get clicked,” said Sainsbury. He suggested automatically checking if an update is available, and then alerting them directly.

Include a 'send-to-friend' option. Sainsbury said these features are very popular among BlackBerry users, who are keen to recommend apps that they like to friends. “Enthusiasts are pushing these apps to their friends.”

DISTRIBUTION

Spend time on your submission. BlackBerry App World operations manager Jason Laughlin said that around 80% of app descriptions require some changes, which can delay the process of putting your app live. This includes everything from spelling and grammar to making sure that you write BlackBerry rather than blackberry. Laughlin also said that developers should try not to be long-winded, and offer snappy descriptions that zero in on the key selling points of an app.

Screenshots are important. Laughlin also warned that developers don't always get it right with their screenshots, especially when they submit a shot of their app running on the BlackBerry simulator, showing a handset skin as well as the screen. “What we're really looking for is just the screens without the BlackBerry shell,” he said. “Believe it or not, that one step is one of the major things we have to follow up with vendors.” He also said that 3-4 screenshots is the most common amount, although developers are able to submit up to 16. Either way, the key is to focus in on the key features of an app, and show them off.

Try & Buy models are working well on the App World. RIM technical specialist Ryan Hearty told developers in one session that a single app using a try and buy model may work better than two separate versions – a paid and a lite. “Right now, Try & Buy is probably the best way to do it without littering the store with multiple copies of your app,” he said. “You're disconnecting them – users are not necessarily using your free app and then going back to find your paid version.”

Don't focus on one distribution channel if others are available. BlackBerry is very different to Apple, in that there are third-party sites like Handango, MobiHand and even direct sales. It's worth trying all of them, even though the App World is clearly driving a lot of sales for developers.

MARKETING AND PR

Get your hands dirty with marketing. “Your greatest concern is not piracy or the competition, it is absolute obscurity,” said Sainsbury. “A lot of developers create an app and think listing it on the store is marketing, and their job is done. But you need to be pro-active with your marketing.”

Consider price promotions. Sainsbury pointed out that selling an app for 99 cents for a day can be a great attention-grabber, when distribution channels support it. Again, this is something iPhone developers are well aware of too – the so-called Peggle effect, after PopCap's popular casual game which rocketed up the charts due to a 99-cent promotion.

Bloggers are important. Again, people were falling over themselves to talk about the CrackBerry effect, where a news story or review on that one site can create a big spike in sales. Identifying the sites capable of giving you this kind of boost is important – and worth spending the time to email them personally, rather than with a form letter or press release. “I spend countless hours emailing random bloggers and tech writers,” said Watkins. “It is crucial.”

Don't just PR new apps or major updates. A couple of developers talked about the impact of just emailing a few key blogs when even a minor update was out. Marcus Watkins released version 2.1 of PodTrapper, and saw sales multiply seven times after a couple of sites wrote about it – even though it wasn't a major update.

CUSTOMER SERVICE

Talk to your users. Frequent forums – CrackBerry seems to be the popular choice in the BlackBerry world, as well as BlackBerryForums. Give out free copies to people and get them to spread the word. Word of mouth is important. iPhone developers giving away promo codes on Twitter also falls into this, although that's only targeting people who follow you.

Have an option in your app for users to contact you. This came through strongly during the BlackBerry DevCon as being important – not only to have a menu option to contact the developer, but to then devote time every day to replying to and acting on those emails. However, Sainsbury pointed out that this can stretch your support team, due to the culture of BlackBerry users. “Often, you'll send a support email, and get a reply back five seconds later,” he said. “They're so used to the immediacy aspect, they're a different breed of people.”

Capture data when getting feedback. Rather than just solicit emails from users, capture data about their device at the same time. On BlackBerry, you can get info like what handset and OS they're using, what operator they're on, and what version of the app they're using. It makes sense to get this automatically rather than get them to supply it.

Analytics are important. During his talk about the 7digital Music Store, DevelopIQ's James Shannon sang the praises of Flurry, whose technology his firm uses to track every user interaction within the store app. “Analytics is really the key to understanding your users,” he said. “We track users' progress through the app so we know which features they are using, and even how long their downloads are taking.” He pointed out that not every user will take the option of contacting the developer if they have a problem with an app, so analytics can help pick up on those issues.

Monitor reviews on app stores. It can be a way of spotting a problem that's just cropped up if several people in a row criticise the same fault or bug. Sainsbury said the evidence so far shows BlackBerry App World users are very sensitive to reviews - “If the latest review of an app is one or zero stars, that can significantly impact sales,” he said. All the customer support stuff above helps to head this off though – if people have easy ways to contact a developer with their problems, they're less likely to use a negative review as their outlet to grumble.

Got any additional tips, or want to expand on or disagree with the ones above? Post a comment and share your thoughts!