How to crack walnuts?
At my house we use a butter knife. At the bottom of a walnut, there's always a small crack that we can slip the tip of the knife through, then twist the knife by the handle and the shells come apart. The little separator in the shell can also be easily removed with the butter knife.
But other than that, we sometimes opt to simply grab two walnuts, and with our two hands, crush the shells against each others, and one of the two walnut shells will Crack and give way. Disclaimer: this method can get messy.