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Research In Motion's (RIM) CTO David Yach addressed a crowd of roughly 700 mobile application developers and others at RIM's first BlackBerry Developer Conference in Silicon Valley, Calif. today, offering up a list of 10 tips to help those developers create valuable BlackBerry applications.

Here are Yach's tips, in reverse order:

10) Device Specific Features: Yach says applications that offer functionality that's specific to a user's device model are usually more attractive than applications that provide few or no custom features. For example, a local search application that can employ the device's native GPS features to determine a user's location is quicker and easier to use than a search app that requires a user to submit a zip code or the name of a city to find local results.

9) Responsive User Interface: Great BlackBerry applications have users interfaces (UI) that are speedy and responsive to user commands, Yach says. For example, an alarm app that displays a confirmation dialogue window after settings are modified is more effective than one that simply saves changes without notifying the user, because there's no question as to whether or not the modifications were made.

8) Available Offline: BlackBerry applications that use "push" functionality to draw information from the Web or other sources and then save that data whenever the app updates are significantly more valuable than apps that need wireless connectivity to function, Yach says.

"Wireless is inherently an unreliable medium," he says.

RIM CTO David Yach at the BlackBerry Developer Conference

Inevitably, users will find themselves in situations in which they want to employ a specific application in an area with little or no wireless coverage; in a basement or concrete building, for example. Unfortunately, they'll be out of luck unless the applications updates themselves and store those updates on BlackBerrys, even if users arenâ¬"t employing them.

Viigo, the mobile RSS reader for BlackBerry, is a great example of an app that stores updates on users' devices, so content can be accessed without wireless coverage.

7) Use Network Judiciously: Yach stresses the word "judiciously" here, because he says proper use of wireless networks isn't just about efficiently compressing data before sending it back and forth between BlackBerrys and the Web. Rather, the concept involves considering whether or not that data really needs to be sent at all, as well as how frequently.

For example, a mobile weather application may update itself every hour, even if the current conditions haven't changed in days. This represents inefficient use of the wireless network, since there's really no need for that data to be sent. An app that judiciously employs wireless resources will frequently provide a better overall experience without putting as much strain on the network, Yach says.

6) Leverage Push: RIM was the very first company to employ the now-industry-standard push technology that enables BlackBerry users to retrieve e-mail and other data without ever having to physical "fetch" it from the Web.

"Push is everything, and push changes everything," Yach says.

Push means that BlackBerry users never have to go looking for new information; it comes to them, he says. Such functionality completely changes the way users interact with their mobile devices by reducing the frequently with which they need to physically seek out new information.

A quality push application also uses the wireless network judiciously, only delivering information when necessary or when users call for it, he says.

5) Preserves Battery Life: Great BlackBerry applications don't degrade the overall performance of the device, and that calls for effective use of the battery, according to Yach. No matter how valuable an application may be, if it reduces BlackBerry battery life to only a couple of hours, it'll probably hurt users more in the long run that it will help them.

"The best wireless apps use wireless the least," Yach says.

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