Keep applications lean and optimized for the speediest possible performance. Animations are fun, but they're a bad idea if they're just a frill. Even the more technical users probably aren't browsing. Someone using a mobile phone to make travel reservations is probably stuck in an airport someplace, not relaxing at home. Design and test with the end user in mind, because a person annoyed by your application probably won't ever try it again.
Mobile devices differ.
Not all devices have the sample capabilities. Make sure to test your application on all of the target devices you intend to support. A few years from now, most people could be accessing the Internet through their mobile phones instead of using a desktop computers. In fact, in Japan that's already true. WML gives you a powerful new way to make your Web applications available to these users, whenever and wherever they go.