For running application directly on the device while developing it, we need to change some options during building the application from Eclipse. Lets see what changes we need.
Settings on device (mainly android device):

On the home screen, go for the Menu button below the screen and tap the “Settings” option. Now, Choose “Applications” and look for “Development”. Then check the box for “USB Debugging” to turn it on. Finally, then connect it to your computer via USB.

First of all, open the application in eclipse. Now go for “Run Configuration” on the drop down menu of Run. Then right click on “android application” on the right side and click new. Fill the corresponding details like project name under the “android” tab. Then under the “target” tab, select “launch on all compatible devices” and then select active devices from the drop down list. Save the configuration and run it by either clicking run on the ‘run’ button on the bottom right side of the window or close the window and run again.

Now while the application is running on the device, you can watch the log on the “log” tab of the eclipse’s console