Best way to calibrate Macbook Pro display?

Hi. I'm an FC editor. I do web videos. I'm on a job where getting the whites just right is key. I've color corrected before with good results on my macbook pro, but this time I want to avoid the nagging feeling that maybe the colors are not exactly what they seem to be. Advise anyone? Is it enough to use the calibration tool mac's system preferences? Or do I need to buy calibration software/hardware?