Animation Pipeline - Pre-Production

Before officially working on an animation, planning is made at the start. Its is useful to plan out every bit of detail you want in an animated film. The Pre-Production system is divided into 4 steps, and are made in the following order:

Storyboarding
Like a comic strip, a storyboard is simply a visualisation of your story, including every scenario and what the characters are doing. The storyboard should be more clear on what actions you what the character the make, and also point out if there are any camera movements you want to help bring more life into the scene.

Layout
When you have made your storyboard, it is then moved on to be examined by the next department. they make sure to understand what are they need to design for the animation. These are usually for costumes the characters would wear, and what are the locations and how are they displayed. Once they get an idea of what to design on on the location or character, they need to draw out a few different suggestive ideas, and then make a comparison to see what could be added or changed. once its finalised, it'll be moved on to the next department.

Model Sheet
A model sheet is an important part for character design. In a model sheet, you need to show the proportions of your character as shape and size, and how they would show their emotions. Basic models sheets consist of the full-bodied character showing the front, side and back, and at an angle in-between them, to show how they would be turning at one hundred and eighty degrees. This part of the model sheet can also be made for a head-turning formation. if there's a particular colour scheme you want for the character, you can add a section to the sheet showing what colour is specified for each part of the character, like their skin colour or what mix of colours are suited to their clothes. Once the model sheet is done, it shall be taken to the next stage where the final character design will be modelled.

Animatic
After you've planned out your entire pitch, you want to compile a animatic version of your film. This gives a rough idea of the film you have in mind. With an animatic, it will help the directors get an understanding of how everything in the scene is set, and also explain how long each part of the scene needs to be timed. You can use a counter to show long in seconds each frame would last, as well the length of camera shots and the character has for dialogue. The animatic is then shown to the director, and will be examined by the team to discuss any changes that may have to made to adjust to balance the timing and progression of the story.

After each of these tasks have been made, and the idea has been approved by the production team and its directors, the film will be taken further into the next stages in the Production pipeline.

Here is a good example on a step-by-step guide on how the animation pipeline works for a 3D/CGI film:
http://cg.tutsplus.com/articles/step-by-step-how-to-make-an-animated-movie/