What is the best way to learn mobile app development (iOS / Android / Windows Phone)?

What is the best way to learn mobile app development (iOS / Android / Windows Phone)?

Android Developers is probably one of the best places to start. I would go about learning the content relevant to Android in the following manner: 

1. Get used to the Android SDK and Eclipse. It can also be done with Netbeans but I don't think that it has as many features. And since most people use Eclipse, it will have better support. As mentioned earlier, you do not need to restart the emulator each time. I too wasted a lot of time on this. Try testing on a phone. It is much faster. You can also try running an x86 image (I haven't the used the emulator in a while but I think it's there in the repositories. Otherwise, you can try Android-x86 - Porting Android to x86. Get used to DDMS. It has a file, thread & process manager for your emulator/phone. It can also be used to emulate phone calls and messages on your emulator.
2. Learn about how to program various layouts. Getting visual confirmation that your programs are working are probably one of the most motivating things. And you'll need to learn what layouts are available and which will be best suited for you so you might as well start with it.
3. Deal with various parts of the OS. Start with the ones that are relevant to the app you are coding. The Android OS is enormous and learning all the API's will take a long time. So don't wait till you learn it completely to start coding!
4. If you want to publish the application, learn about the standards that need to be met. It's not much for the Google Play store. It is primarily related to the Icons and whatnot. But they do have some UI guidelines, which if you follow, will help provide some consistency in Android applications (Like what the Windows phone does).

answered by Ajay Kannan on Quora.com