It's like the old joke:

*How do I get to Carnegie Hall?

Practice.*

If you asked 5 different artists that you admired, you'd get 5 different answers. Some people use only Poser and get stunning renders. Others import their work into Photoshop, while some import the meshes themselves into higher end programs like 3D Studio Max or Lightwave.

Trust me, if there was a simple answer, people would be selling the secret and becoming millionares.

Here's some suggestions:

• Take a picture you like and try to imitate it. Look at the composition, the lighting, and the coloring and see how close you can get to the original. You can also try to recreate a real world picture, such as a painting in the library.
• Contact the artist who made the work and ask them if they have any special techniques they used for that picture.
• Concentrate on one aspect and read everything you can on the subject. For example, pick up a book on lighting. Open up Poser, or another program, and experiment with a simple model, trying lighting from all sorts of angles. You could do the same with color, composition, etc. Once you get comfortable in one area, expand outward from there. Don't limit yourself just to digitasl art books, either.
• Take an art class. Art theory is useful in any artwork.

Hope this helps.