What is the best way to color correct?

There are some great tutorials on YouTube for how to use color wheels and curves, but I'd also recommend free 3rd-party plugins for increased grading functionality using LUTs and presets.

It really depends on each individual. I like to use a plugin called FilmConvert - just as a base. It is a film emulation plugin that incorporates your camera and what color profile you shot in. (Log, Raw, etc.). Once I do this, I add a color board effect, and make sure it happens before (above) the film convert plugin. I will adjust exposure and balance my color. Were the highlights too yellow? Too magenta? Too blue? You can even open your vectorscope as you adjust your color from the color board. After you balance color, you can then add your personal taste to it. Maybe you are stylizing it and you want to alter colors differently instead of perfectly balanced. That's when it's fun, and all subjectively yours. Don't forget that you can add a hue/saturation adjustment as well. These are great for making specific tones in your image different. Maybe the green shirt was so bright, but everything else in the frame looked balanced. You can use the hue/saturation tool to select just the green tone, and adjust the hue, luminance, and saturation.

Yes to Youtube: https://www.youtube.com/watch?v=NxEVQaQ2Y1E

Youtube got me through all my FCPX trouble shooting. This video briefly explains using the color board. https://www.youtube.com/watch?v=CC2L-Ec8GTM