The film is first drawn on regular copy paper at a good old fashioned animation drawing table.
All the sheets are holed and are threaded on a pegbar so they will be in correct position to each other.
(As an alternative one can use 3 thumb tacks and pin them through a stiff strip of cardboard which is
taped tight on a light board. Each sheet that shall be drawn upon is pushed down on these tacks which
are pointing upwards. The same holes are used when filmed.)
Sheet after sheet are placed on top of each other and for each sheet the figures are drawn almost
identically with a pencil (nice to be able to erase) with the exception of what is supposed to move.

It is the differences of each drawing that makes the movements and what tells a good animator from a bad.
The timing is the most important thing. An important tip is to dear to hold the pictures steady once in a
while. Often too much is happening at once and then it is difficult to grab what is really important.