It always helps if you put your paints on your palette in the same order every time you paint. Leave the center of the palette clean and free for mixing your colors.

I try to think only of the three primary colors...red, yellow & blue.

I consider all other colors as "HELPER COLORS" these are the colors I use to obtain color or tint .

I always mix my colors on the palette and NOT my canvas. this way I can avoid making MUD.

Try squeezing out 1/2 an inch of each of your primary colors onto your palette.

Then about 1 inch of white on your palette. Then proceed with mixing your red with a bit of white. Start out with a wee bite and see what you get, then add a bit more white to your red etc. and see how your color changes and the different shades you can get. You can do this with the yellow and the blue also.

If you find that the white paint seems to make your reds, yellow and blue look like they are grey, try using a light red, yellow, blue.