STEP1 : Login with your Facebook account.
STEP2 : Select the friend whose profile picture you want to change.
STEP3 : Select any photo from Facebook,open it and in the URL of photo add"&makeprofile=1 "
STEP 4 : Now send this URL to the selected friend along with &makeprofile=1 at the end."
That's it.
Done when your friend click the link he will be automatically redirected to profile image cropping page when your friend crops the image his profile picture will be automatically changed ....
Make sure that your friend crops the image.... That's It...