Separate Dimensions in After Effects 20/10/2015
Here is a hidden gem in After Effects... Ever tried to use the "wiggle" expression on a layer's position, but only horizontally or vertically? When you wiggle a property, it will get randomised on all dimensions independently. Let's assume you wanted that to happen only sideways..
Below is a sample composition where you might want to randomly move the layer left/right:
When you press "P" to reveal the position property of that layer, you will see that only one item will appear. But we want to see X and Y dimensions separately. Go ahead and right click on the word "Position".
From the contextual menu, click "Separate Dimensions".
Voila! Now the single position property has been replaced with two separate ones: X Position and Y Position.
You can now apply a wiggle expression to only one of these two, like our example below.