Quote: "What is the common meathod to world creation, model creation, ect."
There are many many different ways to create a 3D world, alot of which will depend on the type of game you are making.
If you are intending to create a large 3D game, I think most common method (at least what I usually do) is to create your own "World" creation tool (a level editor) which consists of loading and placing models and other game elements, and then save that out to a file in a format which your game engine uses to recreate the level at runtime.
If I were you, I would check out the free software that is out there and see what you like. Then if you decide to purchase software you can choose programs which do things that your free tools can't.