I'm not sure there is an easy way. The Virginia Institute of Marine Science has this web page:
http://web.vims.edu/adv/ed/crab/pick.html
Crab picking knives:
http://www.google.com/search?q=crab+knife&hl=en&biw=986&bih=609&prmd=ivns&tbm=isch&tbo=u&source=univ&sa=X&ei=dRtvTtzDG-eQsQKGsoTpCQ&sqi=2&ved=0CF4QsAQ