Go out to I-93 and head north.  The highway will run right through the middle of Franconia Notch State Park.  A lot of brown attraction signs will direct you to swimming, camping and hiking spots.  This is where the Old Man of the Mountain used to be.  Then it fell!  Long gone now.  All the following trails are in Franconia State Park.  They are clearly marked with signs and represented on the Franconia website referenced above.