Color Checking

Sample of color checking papers

I am working on a triptych of canvases that are 18"x 36". When I get excited about a painting I just want to start! But I made myself slow down and spend some extra time planning before I started painting. With this size canvas, making a mistake on the color I'm using could cost a lot of time and money. I am painting a scene from the Farmers' Market with a booth of geraniums in bright sunlight, so I want to keep the reds and greens clean and intense. I spent about an hour looking at my reference photo and going through my colors and deciding on a palette. I painted samples on the edge of paper so I can hold it up to the reference or the painting. I also made notes as I mixed the colors and I can now file the papers away for future use. Dave the Painting Guy showed a different kind of color checker that he saw on The Carder Method website. (There's a very short video clip that shows how to use it)

So far this has been working great for me. I find that I am feeling much more confident as I paint and since the decision for the color has been basically made, my mind is free to focus on other things.
Do you have any methods for picking a palette or checking your color?