Stop Motion Filming Technique
The Classic Methods:
One way is by using miniature sets with the puppets(actors) and then shooting the live footage in the background with a projector. Using this method you could get moving "real" people in the background and clay characters in the foreground. With the cost and effort of building a miniature set most people don't use this method.
The most widely used form is called split-screen rear projection. Using the projector scenes would be shot on a plate with a glass sheet placed in front. Then the puppets movements and positions would be calculated. Black paint would be used to block of the areas on the glass that the puppet would cover. The actor would be placed between the glass and the plate and animated. Once all the animations were captured on film would be reexposed to the areas that were masked off before. This created the illusion that the puppets were interacting with a real action world.
The New Computer Methods:
With the invention of the computer and editing techniques it has been a good and bad thing for claymation. The good, it allows people to easily edit and put together claymation movies without using some advanced filming techniques. The bad, people like to create 3D computer animated characters instead of clay characters. CGI(computer genearated images) is much easier to work with because you just need to know how to use the 3d editing program, which is not that easy in itself, and the computer. Anyway back to using the computer to make your movie. Now instead of building a set with miniatures or using film and glass plates all you need is a chroma colored background and something(a nice flat surface is good) for the characters to stand on.
With the cloth in the background use a camcorder w/ snapshot ability to take a picture of your actor, move anything you need to move a little bit, take another picture, and continue until the scene is done. If you do not have a snapshot ability just turn the camcorder on for one sec and turn it off, this will be edited later. Once you have all your video on tape take the camcorder to your computer and hook it up to a capture card. With the camcorder all hooked up use either a video editing program or the program that came with the capture card and save all the video onto your computer. Than with the video editing program import all the clips, the background clips, and any audio you want. Now chroma key out the cloth and put the clay actors on top of the background clips, match the audio, and ta-da you have a live action-claymation mix.