|PRINCIPLES OF ANIMATION
SHOWING A THOUGHT PROCESS
Each one of those drawings must convey the action of the character and also what the character is thinking about. If the character is just moving from one position into another, it will look dull and uninteresting. If you add some subtle actions or pauses for the character to think about what is going on, it changes the audiences reaction to the character.
What is important here is to allow enough time for it to look as though the character is thinking about something. Take the "Step Up/Step Down assignment for example, When the character is at the top of the stairs, they must think about how they will get back down. When you think, you are actually talking to yourself in your brain using words. If you were the character, what would you say to yourself? "O.k., I made it. Now to go back down the stairs." How long does it take to think these words? The same amount of time it takes to say them audibly.
If you have a watch, say those words out loud and time yourself.
How long did it take you?
It took me about 4 1/2 seconds.
Therefore, in your animation, when your character comes to a stop at the top of the stairs, there should be a 4 1/2 second (108 frame) pause.
Don't have them simply freeze though. At the very least, make it an animated hold. It would be a good idea to put them into an interesting "thought" type of pose - hand on chin, scratching head, crossed arms, hands on hips, looking down the stairs... something like that.
If your scene is more detailed, with facial features: eyes and mouth, you can convey thought process through a change of expression that reflects the words the character is saying to themselves.
If the character was thinking, "No, that can't be right!" you'd have them pull back and do a subtle head shake with an expression that matches.
If they then thought, "Ahh, I know now!" how would they move their head and what kind of facial expression would they use?
Just these two phrases with a slight pause between them could be animated in 5 - 6 seconds or 60 - 72 drawings.
Give it a try.
In every scene that you animate, try to incorporate some form of thought process into it.