Here are a few tutorials. Most of these are old, and appearance of surface pane has changed, but most of what they say are still valid:

Surface pane:
http://homepage.eircom.net/~neilvpose/ds-settings.htm

How to make custom MATs for DAZ Studio:
http://mtdremer.hubpages.com/hub/How-to-Make-Custom-MATs-for-DAZ-Studio

Fixing Skin Surface Settings in Daz Studio - Largely about fixing Poser material to work in DS.
http://www.calida3d.com/tutorials6.shtml

My simple summary:

These are just general guidelines.

Diffusion:

This is what controls the response of the surface to diffuse light.  Usually there is a 2D image and a color. For most objects this controls a lot of the appearance. You don't have to have a 2D image. You can just set the color, but then the object will look very uniform and not realistic. The 2D image allows for color/patern variation over the surface. Usually the diffusion strength will be 100%, except when using SSS on skin, where diffusion may be as low as 50%.

There is something called the UVs which map the 2D images on to the 3D object surfaces. Some products have "templates" available that show you where the UVs are on the 2D maps. A big issue with making texture maps is that the UVs warp around the 3D object and at some places there will be seams where the maps meet. It is important that the texure maps line up at these seams, otherwise the seam will be visible in the render.

Specular:

While diffuse light comes from and is reflected off surfaces in all directions, Specular light comes from a single direction and is reflected off in a single direction. Specular light is handled separately in 3Delight. Most primitive lights emit both diffuse and specular light, but you can set them to only emit specular or only emit diffuse light. Specular light is what produces the shinny spots on a persons skin when you take pictures in bright sun light or using bright flash.  Different shaders treat specular differently in detail. There is a glossiness parameter that controls how shiny the suface looks. High glossiness means highly glossy surface and small, sharply defined specular highlights on curved surfaces. Specular is usally white light, but many PAs use light blue or some other color.

 
There can be a strength map, a B&W 2D image. This strength map is frequently put in the color rather than using it as a strength map in the specular strength, but you will see PAs doing it both ways. The strenght map modifies the shaders build in model of how the surface response to specular light.

Some shaders have 2 different specular settings. This can be used to model more complex surfaces, like skin, that may be very glossy in some places and not as glossy in others. Most shaders allow strength maps on glossiness parameter too, but you don't see this used very often.

Surface hight adjustment:

Bump, displacement and normal maps are used to model small surface features without creating polygons to model them. 

A bump map is a B&W map the is used to simulate small hight variations in the surface by making places darker or lighter. If you find a PA using a color bump map, that just means they were too lazy to convert the map to B&W.

A displacement map is a B&W image similar to bump map, but displacement maps actually move the surface points up and down along normals to the surface in the rendering program. This makes displacement maps more expensive to render, but more accurate in modeling.

A normal map is similar to a displacement map but it is a color image with the RGB values corresponding to X, Y and Z displacements of surface points. This allows more complex and realistic variations in the surface because you can move points in 3 direction rather than just one. Normal maps are more rarely used and they can be very expensive in rendering.

SSS

SSS stands for subsurface scattering. It is for modeling surfaces like skin that have a semi-tranparent suface layer and deeper colored layers.  This is complicated subject and different shaders do it differently.   The one think I would point out is that DAZ Studio and Poser support of SSS are completely incompatible. If you have a poser character that has normal and SSS skin materials, the SSS is probably Poser SSS material. The Poser SSS material will apply in DAZ Studio, but the results are usually poor.

Reflection

In addition to specular shaders have reflection settings. If you want to make a mirror or very mirror like surface, you need to use reflection. You can provide a color image of what you want the surface to be reflecting or you can let the reflection ray trace a reflection of the other objects in the scene. In the later case, you need to have other objects in the scene so there is something to reflect, like a sky dome.