Start+Select bring up a menu with the options "Continue without Saving," "Save and Continue," and "Save and Quit." A+B+Start+Select resets the game.
The fastest way to reset the game is to do Start+Select, select "Save and Continue," then do A+B+Start+Select to reset.
Saving and Quitting brings you back to the entrance of the last building or cave that you exited or to the entrance of the building that you reset in.