How to fix AppStore login on iPhone / iPod / iPad

I think most of you had suffered after changing the account on you iDevice (iPhone/iPod /iPad) old account pop up while updating or downloading any app.
I was very disappointed  and restore my Device and set up as new device. Today a Srilankan friend  experiencing the same so I dig out the issue and find some interesting thing, actually iTunes stores last authorized account and while sync the iDevice it push the login information to the device may be the one you don't want.

How to fix it ?
Simple
ON PC iTunes

1. Login with the old Account from Menu > Store  > Sign  in
2. Then Menu > Store  > Deauthorize This Computer
3. Then Menu > Store  > Sign out
4. Menu > Store  > Sign in with your new account
5.Then Menu > Store  > Authorize This Computer

On iDevice
1. Go to Setting > Store >
2. Tap on Sign out
3. Go to Setting > General > Reset
4. Reset Local warning, Home screen Layout and Keyboard Dictionary
5. Reboot the iDevice

Last step
1. Connect the iDevice to PC and Sync with the iTunes

Done