Source of these Expressions can be found at Adobe Help Forum:

https://helpx.adobe.com/au/after-effects/using/expression-basics.html

 

5. Bounce Expression

Create a slide in animation from left to right then paste the below code in too make the animation bounce.

n = 0;
if (numKeys > 0){
n = nearestKey(time).index;
if (key(n).time > time){
n--;
}
}
if (n == 0){
t = 0;
}else{
t = time - key(n).time;
}
if (n > 0 && t < 1){
v = velocityAtTime(key(n).time - thisComp.frameDuration/10);
amp = .06;
freq = 3;
decay = 5.0;
value + v*amp*Math.sin(freq*t*2*Math.PI)/Math.exp(decay*t);
}else{
value;
}

 

4. Time Expression

Simple but effective time expression that lets you control the time or speed an animation plays out.

time*10

 

3. Smooth Expression

Apply this to your animation if you have hundreds of rough keyframes and you want to quickly smooth it all out.

smooth(width = .2,samples =15, t = time)

 

2. SourceRectAtTime

This expression will copy the the width and height of another layer. This is useful when creating an auto expanding box.

s=thisComp.layer("YOUR TEXT LAYER NAME"); x=s.sourceRectAtTime(time-s.inPoint,true).width; y=s.sourceRectAtTime(time-s.inPoint,true).height; [x,y]


 

1. Wiggle Expression

Just copy and paste this code onto the position property of your layer to create a handheld camera look. 

wiggle(5,10,1,.5)