First off: making the 3D model.
Usually, when designing a static 3D, it only needs to look good on the outside. It doesn’t matter when parts are just barely holding together or when the inside of a leg, for example, intersects with the hip. When designing something that will eventually be animated, you can’t do those things. Everything needs to be placed in a way that it can rotate and move around its axis, without any errors. This took some time to get used to, but because I made a robot, everything was really straight forward and clear. All of the joints were designed in such way, that it only could possibly move in a single direction. This prevented any mistakes later on.
In this step I already had to take the rigging in consideration, because the joints will be linked to the armature. Everything had to be symmetrical and logically placed, in order to make it look somewhat natural.
The materials I used in this model were quite easy to do. The big parts like the joints, the head and the body had to be a plastic looking green material and the connecting bones were supposed to look like metal rods. This came out quite realistic.