Most boots have an apparatus on the back that softens or stiffens the boot's forward flex using a wrench provided in your bag of goodies. Some use flex-adjustment modules that can be inserted into the lower shell in a way that stiffens flex. Consult your owner's manual for details. "Most of today's boots come pretty soft out of the box," says Gleason, "but a larger or more aggressive skier might want more structure from the boot, which gives you more leverage over the forebody of the ski for quicker bite." If you're not sure, try the boot first.