What is the best way to calibrate your monitor for a web designer?

I have a Macbook Pro that I use as my main computer but also connect it to a 22.5 inch LG widescreen monitor as well. I notice that the colors on the LG always seem to come off a lot different than on my MacBook Pro. I have tried to go through the monitor calibration multiple times and still seems off. Just thought I could get some feedback on some good solutions or what has worked well for others. Thanks!