How do I use a hit and hold circuit with a solenoid?
This is a 'hit and hold' strategy for use in induction coils. The hit is to apply all of the current to the solenoid with a higher voltage, the hold is to apply a lower amount of power with a lower voltage. The way I have switch solenoids in the past is this:



So the idea is you hit the solenoid with a higher voltage momentarily and then back off the current with a lower voltage (or resistance in series). However

Q1 is switched on first, then switched off momentarily (this can be timed) and then the other gate switched on. There is a schottky diode to prevent backflow in case a software switches both fets on at the same time. 

If your using a micro controller to drive the lines you can use a pull down GPIO port and tie the pins to the rails ( and you might want to put in a protection diode)

I have used DC to DC converters to drive the rails, for example I'll use a 12V rail for the high voltage and a 6V rail for the low voltage, which will give you roughly half the current for the holding current. You'll need to look at the solenoid and its holding current to choose the voltage for the high and low voltage.