Crack the nut!!
Ha ha...pal, i am surprised why no one has replied here. Yes indeed it is a daunting task to crack it open. When we were young we used to open it by putting it in the door keel and close the door. Had many a times jammed my fingers

But now a days we buy the broken ones itself, hmm... save my fingers!
That should be one good way, other wise put the walnuts in a bag and take a hammer and hit them hard, that way it will crack open.
Happy eating..and tell me how you did it too!
Poornima