How to build an APK file in Eclipse?
When you run the project on the emulator, the APK file is generated in the bin directory. Keep in mind that just building the project (and not running it) will not output the APK file into the bin directory.
For testing on a device, you can connect the device using USB and run from Eclipse just as an emulator.
If you need to distribute the app, then use the export feature:
Then follow instructions. You will have to create a key in the process.
There is no need to create a key and so forth if you just want to play around with it on your device.
With Eclipse:
To export an unsigned .apk from Eclipse, right-click the project in the Package Explorer and select Android Tools -> Export Unsigned Application Package. Then specify the file location for the unsigned .apk.