Acorn shell thickness varies from tree to tree. Tan Oak acorns are hard to crack open, while California Valley Oak acorns have a thin shell, that dries and splits open, allowing easy removal of the acorn.
The cracking method I’ve settled on for hard-shelled acorns, is to use the “Texan Nut Sheller.” It’s a hand-held pair of pliers with a sharp blade. It’s a dangerous tool around children but a must-have for acorn enthusiasts.
Whatever you do, have fun with acorn gathering. And don’t forget to make an acorn chocolate cake! Suellen Ocean is the author of Acorns and Eat’em, a how-to vegetarian cookbook and field guide for eating acorns. Find it here: http://www.amazon.com/Acorns-Eatem-How–Vegetarian-Cookbook/dp/1491288973