Lets animate a thing.

So here's our character.

A simple ball with a tail. Pretty easy to animate. The first thing you want to figure out is what the character is going to be doing, because there are millions of possibilities. For the sake of time I'm just going to have him hop into frame, stop, jump a few times, and then leave.

So first I need to figure out the blocking, or where the character is going to be in the shot. To start, I'll draw a frame where the ball comes in.

Where it stops.

And then where it exits.

Now I'll add in the jumps. What I'll do is draw a frame for the ball when it's in the air, and then one for when it touches the ground. I'm not going to add the tail yet because I want to concentrate on the ball first. It's best to worry about one thing at a time .

Now I'll put in the anticipation drawings, which are basically when the character squashes down before it jumps. Anticipation drawings emphasize a movement by showing the character building energy, like how a you bend down before taking a big leap or a boxer pulls back their arm before throwing a punch.

Okay, now I'll add drawings that show the ball moving into and out of frame. These will basically be of the ball moving up and down as it moves into and out of position. I'll also squash the ball when it's on the ground to anticipate the jumps.

 It's important to make sure the ball stays in the air long enough for it to read as bouncing. I have it staying in the air for four frames, and touching the ground for two. I'f  I wanted the ball to appear heavier, I'd probably have it stay in the air a lot less, and stay on the ground a lot longer. If you wanted it to appear light as a balloon  you'd add more frames when it's in the air.

Now to add the in-between drawings. These are the ones that go 'in-between' the drawings we already have and make the animation look smooth. They ease into, and out of the key drawings, which as the frames we have so far. Since when the ball is bouncing it's in the air more than it is on the ground, most of my in-betweens are going to favor the "in the air" drawings. That way it looks like the ball goes up, slows down as it gets to its highest point, and then speeds up as it starts to go back down, kind of like a roller-coaster.

For the parts where the ball is touching the ground, I'll draw two frames. One where it's on the ground and almost squashed, and then another where its a little more squashed. Basically one frame easing into another.

Almost always space the in-betweens so that they favor one key-frame or and avoid spacing them evenly. Try to create motion that moves in an arc instead of a straight line. Straight lines make the animation look robotic.

So  here's how the animation looks with in-betweens. Notice that I added an anticipation before the ball leaves frame to make the animation a little more interesting.

Now it's finally time to add the tail. I'm doing this last because it's movement depends on the ball's animation. If  I'd done it sooner and then had to change something with the ball, I'd have to change the tail too, which would be a lot of unnecessary work. Now that the ball is pretty much done I can animate the tail by "layering" it onto the existing animation.

For the tail, I'll use the wave principle, which can be used from almost anything from hair, to clothes, to arms, to legs, and even subtle facial animation. It's basically this:

An S curve, a C curve, another C curve moving forward, an S curve, a C curve, and another C curve being moving back.When I put them together I get something like this:

Now if I use the wave principle on the bouncing ball's tail, I get this.

And that's basically it. I figured out the main actions, added anticipation poses, drew in-between frames, and then finally added the tail animation.