I will put an example of a simple sculpture. You can follow the step by step process to make your own experience.
First of all, you have to find a subject. If it's one of your scukpt, take an easy one. It's very important to take a subject you really like. For example you can take a funny character of your favorite comic book, movie, cartoon, video game, website, ...
When you have found a subject, you have to find some reference (some pictures from different point of view). For this example, I have taken a character of an old video game (NeverHood).
To be honest, this game is not a really good one, but I like the artistic direction of doing everything with modeling clay. There is really few video game of this kind. And I think that this character is funny and not complicated.
First step : making the armature. For this step you need some tools.
Draw your character in the cross position (a little bit like the Vitruvian man). Mark all the articulation and the squeletton.
Take the wire and put it directly on the draw. You can use some green stuff to mark the squeletton. Be careful : do not put green stuff on articulation.
Let the green stuff dry...