Controlling multiple solenoids with arduino
Arduino I/O pins, and the output pins of 74HC595 shift registers are logic-level outputs, and are not intended to drive power-hungry items like solenoids. In either case (direct I/O or shift registers) you need to use the logic signal from the output pin to drive something else that switches the 12V source.

That something else can be a MOSFET or a relay, though often even relay coils are themselves driven by a MOSFET or other transistor that is switched by a microcontroller output pin.

One of the many search results that describe this is at http://hades.mech.northwestern.edu/index.php/Driving_using_a_single_MOSFET