There's a great deal of pre-production that goes into any animation and it nearly always starts with a storyboard. Here's an example of a more refined sketch for the Powell animation we did, which quite faithfully represents the end product.
From this stage we produced a 3D animatic so we could work out the camera moves ahead of the greenscreen shot, and ultimately be confident on-set that everything would would work when it came to post-production. Check out the final animation here: Powell animation.