Here is a really useful and informative page detailing the typical VFX work pipeline. The amount of work is quite overwhelming. All the departments are interdependent, and particularly in post-production each is involved in extremely intricate and detailed work. Of course, the pipeline varies on the scale of a project; on a small scale project one person would probably be responsible for many of the different jobs.
The page goes into detail about each of these steps:
It's quite worrying that I'm still in the modelling/rigging stage... This pipeline also doesn't take sound and music into account, which is an important part of creating a good piece of film.
Something I found interesting was how software that you generally associate with VFX and CG work, such as After Effects, Maya and 3DS Max, are often not powerful enough to achieve the results the artists want; therefore they create their own plugins, tools and even entire programs that are catered to their needs. This takes place in the 'Research and Development' stage, and involves the input of technicians, mathematicians, programmers, etc. As creative projects become more technically advanced, people who are more logic and technically minded rather than creative are still crucial assets in the filmmaking process.
There are a few steps I could have worked on to make my film more accurate. For example, in a big budget film a lot of effort is put into tracking and match-moving so that CG elements and filmed elements match up with each other seamlessly. I'm not sure what the focal/aperture length of the camera was at the time of shooting, so I won't 100% accurately be able to place the model in the scene, although in my case it won't make a difference as the actor and model aren't actually in a scene together (the shots with the model will be 100% CG). My main worry will be the shot where the spaceship arrives; I should ideally make a rough 3d sculpt that is to scale of the area where the footage was shot, so that the ship will match it's surroundings, but I'm not sure how to go about that as I won't have any way of knowing the exact height/shape of the buildings. I'll have to rely on judging by eye.