I can DRAW very well but I get impatiant to put on color. Since I love to go out and do photography with my Nikon D80, I developed a method to shorten the drawing time and use my photographs. I take several photographs of the subject: one with a larger view, one exactly framed like I want to paint it, and another closer with more details of the subjects, in case I need them. If I can, I like to back to the same place at different hours of the day to take pictures. I get different angles, light and shade, and then decide wich one I have in mind.

A technique of MIXING COLORS in a conscious maner and not improvised consists of creating a chart that you can consult to get to know all the hues of your palette. This one is of greens; the first square on top at left is created with the yellows vertcaly and the greens horizontaly, that makes the Spring chart, very warm.
The chart below at left, is made with the orange, red and pink colors mixed with the greens, this gives a cool, winter chart.
The 2 charts at the right are made, the top one, from the yellows and the blues, the one at the bottom is made with the greens and the blues. This creates a full range, mature greens that make the Summer chart.

This is an exemple of a grey chart. I ahve greatly explored making grays because I do not like the greys you buy in a tube, I feel they are dull and opaque, and it is impossible to know with what pigments they are made of.
So I set out to practice making my own greys, either soft or textured, warm or cool but always luminous. I place great importance to greys because they serve the purpose to enhance the main colors.

Remember that a grey is made with all 3 primaries; blue, about 70% of the mix, red 20% and yellow 10%.
The exemple you see is made out of cobalt blue wich is not sedemtary so all the greys made with it, will have a smooth likeness. Start by making a "neutral" grey (first square at the left), then add a little more blue, you will have a cool blue-grey. Then, in that same mixture, add a lttle more yellow, you will have a cool green-grey, and if you add a little more red, you will have a warm brown-grey.
In the exemple, there are 3 horizontal lines with different greys. At every line, you alternate the yellows and reds to the cobalt blue to obtain different greys.
Now make the similar exercice with each and every blue you have in your palette! each yellow and ochre! each red, rose and violet!
BRAVO! you will get to be an expert in making personalized greys!
 

This chart is absolutely allucinating! she is 22 x 22  (56 x 56cm)
She has more than 900 little squares!
She has horizontaly and verticaly, all the colors of my palette and all the possible mixes between them. This is the most wonderful way to learn and memorize all the possibilies of one's palette. It also teaches you, as you go along, the ratio of each of the colors in the mix. Exemple; it takes only a lttle bit of red to start making a violet.

You can click on the image to enlarge it. The sheet is devided diagnoly, at the left, wet in wet and right, wet on dry. The # represents the size of the brush. The letters represent the exercice.
A: a line done correctly with the rigger; full of color and lighly pressed on the paper. The line beside represents the bad way to do it; too fast and pressed to hard.
B: a line done with the same rigger done in wet.
C: a line done with a #8 brush in wet, loaded with sedementry pigments.
D: little dots done with the same brush.
E: a line of pale green done with a 2" brush, then some cobalt blue added in it while still wet. Look at the dark green border streching in the paper.
F: a little drop of red dropped in the green still humid*, not wet*. The drop stayed smaller than if in wet.
G: a drop of water on humid.
H: a second line of red done on the first one dry. Both values* add-up.
I: some small rectangle done with a 3/4 flat very upright. The darker rectangles show what happens when you press to hard.
J: a brush wich is too dry, not enough color, makes this scratchy effect that could be wanted to create texture. You have to apply that line rapidly and lighly.
K: what happens when you try to soften the edge with a wet brush, and not a humid brush. The excess water pushes back the pigment to the other border and creates a back-run.
L: a perfect exemple of softenning, there is no line showing.
M: the same line before being softened.
N: a line done with the full range of a 1" flat brush, and some lines done with the thin side.

* the paper is considered wet when it is fuly loaded with water and is shiny looking.
The paper is considered humid when it is starting to dry, does not look loaded or shiny.
* value; the name given to different gradations of a color from 0 to 12; 0 being almost none, to 12 being its darkest before being opaque.

Here is a very easy chart to make but reveales a lot of informations on your palette. Draw a 1/2 inch black line with a permanent felt pen. Then, make a line with each of your colors over that black line. Dry, then try to remove a small line with a damp brush, bloth and dry.
You will discover if that color is stainting or liftable,
you will also discover if that color is smooth or sedemantry if it gives a rough looking surface.
You will also discover if that color is transparent or different degrees of opacity if it makes a veil on top of the black line. In one chart, you can discover all the caracter of each of your colors.

Softening: is the hardest technique to master but also the most important one. It is the ONE that will make you progress and grow as an artist. You have to paint with 2 brushes at the same time; one to apply the color, and the other to touch the edge with water to soften that edge. The brush that touches the edge must be damp not wet; that means it has to contain clean water but not be fully loaded.
When you rinse that brush, you bloth it a bit but not completely. Not that easy to do... but it will make you loose that hard edge and create a soft edge.