Slow up and down

http://screencast-o-matic.com/watch/cDQ2cJjlKx

Making sure the things look more realistic is always the job of a animator.  So in the aspect f stopping and starting in life it takes awhile for something to get a move on. Physics is a part of animation.

Arcs

Arcs are used to help see where the movement is truly going. These arcs can help find out what needs to be fixed to look more natural.  Then using the graph editor can make theses changes very easily.

Exaggeration

Exaggeration is good in moderation. Like most thins in animation, if exaggeration is over done it can the soar on the eye of the audience. In this section, we used just the small movements of the face to tell a store itself. This is what exaggeration can do when used well.

Squish, Squash and Strech

When you squish something it still holds its volume. When animating things you have to remember this fact. If you squish something it doesn't just not-exist partly. This is true in people as well. If you have ever looked at the  Olympics this is clear.

Secondary

A secondary action is a minor and smaller action that happens within the main action. A secondary action does not have to be dependent on the main action. It is something added on to make more realistic. As humans we do many smaller actions at a time.
Ex: eye movement

Follow Through and overlapping

For ever action there is an opposite and equal reaction. That is the basics of follow through and overlapping. When an action of movement happens there is another action that is directly dependent on the first action.

Pose by pose VS Straight ahead

Animating by pose to pose and straight ahead are very different. When doing poses to pose you have the animation set to stepped tangents in the graph editor. This makes you able block it out first and then smooth it by changing to curves afterwards. In Straight ahead you do the curves right of the bat. That best though is to go back and forth between them.