Before we begin this exciting magical journey, it is good to know what you want your sets to look like. Actually visiting such places first hand is the most beneficial, but photographs and concept art can work just fine. What is the mood you are trying to set? What is the scale of the landscape? A trick to making great foreign environments is taking elements from our planet and altering them to suit your new landscape. The best concept artists are able to strike that great balance between familiarity and alien-ness. This link below has some of the strangest looking things on the planet.
here are some pictures of when i went to the grand canyon and death valley:
Simultaneously, it is good to think about what kinds of organisms are going to inhabit the landscape. How are they going to travel across the terrain? What elements will they utilize to live in, hunt for food? In our case, we have a giant bug that lives in a crater, stalks his prey by emanating a poisonous toxin that draws them towards his nest. okay, i could go on and on about visual reference and building your visual library, but at some point we have to begin. So the next thing to do is carefully storyboard your film so that you exactly what shots you will need. This will save you time. Instead of building one massive set with everything inside it, you can build multiple smaller sets that are custom built to fit your shots. for instance, if you have a closeup of a guys helmet on the ground, you would want a seperate set with a larger grain so that it looks very close.
Next it is always good to draw your landscape a bunch of times to see what kind of basic shapes you are looking for, and to work out composition and color. Check out the work of the evertalented Sparth.
it is great to look at professional's work to see what they envision, but at some point you should draw it yourself to get specific to your own needs and to have your vision. You may be a fantastic carver and a poor drafter, yet i still believe that the cognitive process of drawing will inform your carving.
Ok, enough said about that. On to the actual building....