i want to better my understanding on procedural materials but dont know how to go about it? when i watch a tutorial ill understand the texture he uses such as using a noise texture or magic texture but if I had to do it on my own i wouldnt know which texture to use, can someone maybe give me a workflow to beak things down when making a material.
I would start with the Shader Forge series here: https://cgcookie.com/course/shader-forge
The thing is, you can make any material procedurally (depending on your skills/ experience).
With the Shader Forge course you'll have a really good basis (Kent explains really well, why he uses certain nodes).
It is made with older versions of Blender, so feel free to ask if you get stuck or don't understand something.
There is no special workflow, it is mainly looking at reference and recognizing patterns.
And then sometimes you can find something in the Forum: https://cgcookie.com/questions/11248-voronoi-demystified
or: https://cgcookie.com/questions/11163-musgrave-demystified
To clarify what are procedural textures/shaders are, they are mathematical algorithms that generate a pattern. Voronoi textures are based off of math, but you don't need to know the math to find the patterns, like spikey said. When someone says "procedural," they usually mean the default textures that are generated in the program based off the algorithms. Noise, wave, voronoi, etc are procedural textures.
When to use them is down to finding the patterns in the material. If they are repetitive patterns, then procedurals are usually pretty good for them. In fact, in the Shader Forge series, I actually created a hammered metal shader from the water shader because they were similar in analysis. Practice recognizing the patterns and what procedural texture(s) you would use to recreate the effect to help nurture your understanding and observational skills.
Shader Forge is awesome.