Hey, thank you for your feedback. I wasted a lot of time learning Daz, so I will tell you some things which are very important to know imo. It's like, I wished I knew these things right from the beginning.
First of all, you should get familiar with lighting. I assume that you are going to use Iray. Play around with spot lights, place them into the scene, rearrange them, check out the renders. You can play around with commercial Iray light presets which you can get on some of these sites...
Experiment with surfaces. Check out how the figures are built down to the very last bone.
Play around with the sliders in the surfaces tab, place other materials on figures, and make them glass sculptures for example. In this way you will learn a lot about the mechanisms behind this.
One essential thing is the camera. Always use camera in the scene, not only the perspective view. And ALWAYS turn off the camera headlight. Don't even think about turning it on. It's useless and will completely mess up with your renders. The camera is what gives you the "realistic" look. You can also undo movements of the camera which is very handy.
If you want depth of field, you better learn the basics of photography.
I use a focal lenght of 200mm for portraits, which professional photographers also do.
In Parameters->Camera panel, turn on depth of field, then turn on "Near DOF Plane Visibility" and use the "Focal Distance" slider to set the position of the plane. The plane decides the transition between sharp and blurry.
It is not realistic to have the whole scene razor-sharp. The brain will notice and tell that there is something wrong. So use DOF.
Check out Render Settings->Environment. This is one of the most important things. Understand what a dome is, learn the difference between "dome" and "dome and scene" or "scene only" in the "Environment Mode" panel.
TIP: If you are using dome lighting only in the future, use CTRL-L to turn on the helping lights. Otherwise you will see pitch black in the preview window if there are no light sources.
Get some skin shaders like anagenessis and apply them to your figures surface. It will look a thousand percent better just by doing this.
And now a topic which is very important to me: Details.
Try to add as much detail as possible to your figures. Use fiber eyebrows and not the flat brushstrokes which come with the facial texture. For example, these will not create shadows on the face. In real world, eyebrows will throw shadows.
Use the brow remover tool to erase the drawn eyebrows and use oh my brows to apply the fiber. It will look much better.
You can also use fiber eyelashes. It is not a big change compared to the eyebrows but the brain will still notice.
Then, use facial hair like "peach fuzz" this is very important. There is always tiny blond/white hair on human faces.
One of the things I missed at the beggining was the model looking right into the camera.
In case you didn't know, select one eye with the selection tool and go to the "Parameters" tab. There you choose the first entry, the one with the bone. On the right find "Point at" and select your camera. Repeat with the other eye.
Another thing are sliders. Sometimes you have the sliders going from -100 to +100 for example. You pushed it to the maximum in one direction but you need more. Then click on the gear icon that comes on the upper right on every slider and choose "Parameter settings". Uncheck "Use limits" and you are ready to go over 9000.
Now, that's it for now. If you have further questions on a certain topic then let me know. I will try to help.
Now have fun with your renders and let's see the differences between the renders you made before and after applying my tips
Cheers