This last year I took a watercolour class given by the very talented Nicolas Doucedame. While I had always used this medium, I had only taken one class in it, quite a long time ago. Nicolas offered a very clear and simple technique, and I appreciate having worked with him.
First off, our palette was limited to aurelian yellow, cerulean blue and permanent pink (I preferred Schminke’s rose madder for this last); later adding indian yellow and ultramarine. I don’t see the need for any more now. Since I worked for so long in the CMYK printing world of graphic design, the mixing of colours was no problem. The limited palette unifies the painting, and makes things a lot simpler when traveling. Of course, there is the occasional need for a turquoise or different pink (in the tropics for example).
To start a painting, Nicolas splashes an arbitrary mix of the three colours in a primary wash. This base prevents those awkward white spots that make the eye jump around looking at a painting. It also mimics the natural irregularity of nature.
Nicolas also taught me the use of hard and soft edges in every stroke: The defined section supports the focal part of the painting; the soft edge falls back to replicate the natural way we see things (as opposed to how a camera perceives the world).
Most importantly, I am learning to attend to defining the center of interest in the painting. I find it difficult to decide before I start what exactly I am most interested in, but keeping in mind this important aspect has improved my compositions.