One of the big secrets of watercolor painting is water control, learning to get the right value (dark or light) without creating puddles. Puddles are not your friends. Many people think “I want a light blue, therefore I will add more water on my page”. This creates a puddle that takes a long time to dry and is difficult to manage. Alternatively people think “I want a really dark value, therefore I will add more paint”. Again a puddle. Instead of adding more water or paint on the page, change the concentration of paint in the mixture, not the amount of paint on the page.
A good way to practice water control is to create a monochrome painting. Just use one pigment (pick a dark color, dark brown is nice) and vary the concentration of paint to water. As you do, pay attention to the range of values, starting with the lightest, and building toward the darker values, and avoid making puddles on the page. Start with lighter values and make your way progressively to the darks.
Print out the Nuthatch sketch to follow along with this demonstration. Click on the first image to start a step-by-step side-show.
This drawing is based on a photograph by Vivek Khanzode on birdpixel.com.