Power, Ground and a RX data pin that can either hook to your Arduino TXData pin 1 or any pin of your choice when using the SoftSerial library. So, basically Signal Ground and one Arduino pin are necessary for communications. If using Arduino pin 1, Serial.print with the necessary positioning and/or clear screen commands get you up and running pretty quickly on displaying output.
And note that the SparkFun display you mention is 3.3 Volts. If you are using the Arduino 2009, this might be supplied from the 3.3V pin but the current is limited, on other iterations like Boarduinos, you will need to arrange for 3.3V regulated. The spec on the SparkFun board
The SerLCD v2 has the ability to drive up to 1A directly for backlight control or as a general purpose high-power control pin.
kind of worries me, so I'd arrange a separate regulator circuit for it.
Modern Device http://www.moderndevice.com/LCD.shtml
has a 5V Serial Kit I've built with great success that I use for my projects.