It depends somewhat on what resources you have.
I like to output data to the serial port, copy it and then paste it into OpenOffice Calc for graphing. I suppose you could paste into Microsoft Excel and graph it there as well.
Of course, if you have complete control over a graphical LCD, I suppose that you could plot some data there as well.
You need to figure some things out, such as how many samples over what period of time, taken with what resolution and displayed with what resolution. It may also help to know what Arduino you have and what other hardware to which you have access. How quickly you want something done may play a role as well.