Many artists use a whole host of techniques to create different effects within their paintings.
There is neither a good nor bad or right nor wrong way to use them, it is totally individualistic.
For me, I favour counterchange,which in short is changing from one colour to another in any particular passage.
It creates variety, and interest, and is always effective say, when used in large areas of shadow.
I almost have an obsession with it, and it features strongly in my work.
You can notice it in on a smaller scale in this ACEO.
I have used it in the fence, chimneys,roofs and doors.