First of all, editing or managing the build.prop file may be very dangerous, therefore make a backup of your system before you even touch it.
Also note, the walkthrough requires root to work.
Firstly, download the Root Browser. You don't have to use excatly this one but this one's one of the best I've ever had.
Secondly, navigate to the file. The build.prop is located in /system/ directory. Open the build.prop and run it as RB Text Editor.
You should now see some text saying information about your phone = manufacturing number, density, model and more.
Let's change the samsung company name to AndroidHackz. To take the effect, reboot your device (and pray it will boot up).
You can also change and fake your Android version. More info about faking your Android Version HERE.
Next example. try changing this line:
Change the Nexus 4 (Or whatever phone you own) to anything you wish: for example - Nexus 5.
If you navigate (after reboot) to settings -> about phone, you should see the device name has changed - to Nexus 5.
Warning: Changing the build.prop may come handy sometimes - you can run more apps by modifying the manufacturer or model of your phone. Anyway, if you do this, you need to wipe CACHE+DALVIK otherwise the Google Play may not work properly.
Using the build.prop, you can also change your device's density and make tablet from your Android phone: full article available HERE