Color mixed on palette
Traditionally we mix colors on a palette, and then apply to paper.  Here is an example of ultramarine blue and permanent rose mixed on the palette and then brushed on paper.   Usually this process gives a very uniform color result.  

To add a little movement and visual interest, you might consider half-mixing the color on the palette, and then apply to the paper, letting the colors continue mixing on the paper after application.  This can allow for some accidental color variations that can add a sense of movement and interest. 

Glaze
A glaze is a layer of paint.  By applying a glaze onto another color, you can modify its color.   This is a wet-on-dry process, so it is important to make sure the bottom color is dry before applying a second color.  Also, the glaze should be washy enough so that some of the underlying color will show through.  

 In this example an ultramarine blue glaze was applied over a dried permanent rose paint,  giving it a purple cast.  Usually you glaze darker colors over lighter colors.  Transparent pigments work best for this process. 

Color puddles
In this mixing strategy, prepare  3-4 puddles of separate colors on your palette.   Then brush through the puddles with your brush and apply to paper.  As you brush through the puddles, keep in mind the end color you are aiming for.  This"accidental" approach can give you some interesting pigment shifts and add visual interest.

Color mixing wet on wet
This sounds like glazing, except you apply the wet color on top of a wet color.  This is a fun way to apply paint and to encourage dynamic pigment interactions that give visual interest.  The colors here are a wet ultramarine blue over a wet permanent rose.
 

Developing a painting by glazing
Glazing is the traditional way one develops a painting.  In this process, you keep on adding different glazes (layers of paint) to help create a feeling of light,  shadow, and space.   In this example, the entire shed was first  painted yellow.  Then a washy dark  glaze was added to the shadow side of the shed  The addition of the glaze immediately heps to give the shed a sense of  dimension.