This post describes the detail procedure how to debug default applications that comes with Android source code...
Step 1: First launch emulator from command line (by typing Emulator command)
Step 2: Then launch DDMS using command line (by typing DDMS command)
Step 3: Start your application in emulator which you want to debug and you can check the process into DDMS (DDMS will automatically sync with emulator on 8700 port)
Step 4: Start eclipse and open your source project (you will get one error regarding port 8700, please ignore it this is due to DDMS already sync on 8700 port)
Step 5: Put break pointer in your source code to debug it
Step 6: Right click on your project -> Debug as -> Debug Configurations then you will see Debug configuration window
Step 7: Right click on 'Remote Java Application' and select 'New' then give name 'android-debug' or anything you like.
Step 8: Set the 'Project' to your source project
Step 9: Keep the 'Host' set to 'localhost', but change 'Port' to 8700.
Step 10: Click the 'Debug' button and navigate in your application on emulator.
HAPPY DEBUGGING..........