Here are the connections I use:
// Pins for serial LCD interface. For speed, we use the SPI interface, which means we need the MOSI and SCLK pins.
// Connection of the 7920-based GLCD:
// Vss to Gnd
// Vdd to +5v
// Vo through 10k variable resistor to +5v (not needed if your board has a contrast adjust pot on the back already, like mine does)
// RS to +5v
// PSB to gnd
// RW to Arduino MOSI (see below for pin mapping)
// E to Arduino SCLK (see below for pin mapping)
// RST to +5v
// D0-D7 unconnected
// BLK to ground (or collector of NPN transistor if controlling backlight by PWM)
// BLA via series resistor (if not included in LCD module) to +5v or other supply
Your display has a contrast pot on it already, so you don't need to connect the Vo pin.
You do need to have reliable soldered connections. If you solder a header pin strip to the display, you can then plug it into a breadboard.