Steps to Creating a 3D Environment

1. Figure Out a Concept – Inspiration is everywhere, just look around.
2. Gather References – Go to a park, go online, watch films you love, go to a museum…
3. Get a Color Palette – This helps with the mood of your piece.
4. Figure Out Composition and Lighting – This helps refine the mood, readability of your piece. 
5. Block Things Out – Start with simple Shapes and work the details in. 
6. Refine the Blocking - Make a shape that is uniquely identifiable.
7. Model or Gather Set Dressing – This is the details part, add medium details and fine details.
8. Assemble and Refine Your Scene
9. Render It and Post Process It, or Bake It and Export It for Games or Interactive Content
10. Review your image to see how to make it better

Beginner

Cg boost has some ideas about visual interest into your image.

Beginner ideas, intermediate blender skills. Great tips on what to add to a scene to make the scene awesome.

Very good ideas on making a sand environment  - Beginner ideas, intermediate blender skills. Talks about lighting also.

Intermediate

Make a 3d forest Trees that hug the mountain.

Make realistic environments with photoscans  saves time

Make an Mountainous Island Shows how to make a mountain Using Procedural methods.

Make a very nice mountain CGGeek Start to finish Watch this video and then watch the below video

Using what you learned in other videos to make a nice environment.  Cggeek is good at putting together his videos to make a nice Scene.  Watch his previous videos first.

Advanced

Large Scale enviornments He shows how he makes a cool winter castle in an environment

Shows a timelapse of a large scale winter environment being made Timelapse shows the details of placing items and what it takes to make a good environment.  Takes awhile.