I just recently bought this LCD on sparkfun:
LCD-00710
It says I need a 10k potentiometer for the contrast pin. I want to know what negative voltage is, for one. And while I don't have the potentiometer they suggest, can I use this one:
COM-09288
?
Thanks.
I want to know what negative voltage is
A voltage that is negative with reference to the common ground of your circuit.
If you took a battery and connected the negative terminal to ground then the positive terminal would be a positive voltage.
So if you took a battery and connected the positive terminal to ground then the negative terminal would be a negative voltage.
Any 10K to 4K7 pot will do it is not critical.
Would you mind showing me how a potentiometer would go into a circuit for negative voltage? I'm rather new to this.
Looking at the pot here is what you get:
[----------------------------------------]
[ ]
[ + ]
[ ]
[----------------------------------------]
|||| |||| ||||
Positive Adjust Negative
Check your schematic on your lcd you got
From what I can see is
Pin 1 to positive
Pin 2 to negative
pin 3 to adjust(contrast)
The positive is connected to your +5v on arduino
The negative is connectived to GND on your arduinno (any gnd pin works because ground is always ground)
So basically It goes +5v from arduino to pot then that wire or trace to the +5 on your lcd
Then the gnd pin on arduino to the ground on pot then the ground on pot to the gnd on lcd
The adjust goes directly from pot to to pin 3... anybody correct me if im wrong here but from Ive read on this lcd is how it should be hooked/wired/soldered up 
etherit:
If you have not already done so then download the datasheet* from the sparkfun site. The diagram showing the potentiometer connections is on page 9 and the pin definitions are on page 3.
The negative voltage that you need is generated on the pc board and is available at pin 18.
Basically one side of the pot goes to pin 1, the other side to pin 18 and the wiper to pin 3.
Don
Alright, thanks a lot guys, I'll give it a shot.