Making custom presets in After Effects is easy.
Holding shift, select all the keyframes, effects, and properties you want to turn into a preset. Then click the Create New Animation Preset icon in the Effects & Presets panel. Give it a name and that’s it!
After Effects will automatically save your preset as an .ffx file. And you can apply your preset from the Effects & Presets panel.
When you apply a preset the all the keyframes, effects, and expressions will be applied to the selected layer. The keyframes will be applied relative to where the Current Time Indicator is within the comp.
You can use presets to automatically set:
You can even use presets to create shape layers (see Bounding Box).
If you find yourself copying and pasting the same keyframes over and over use a preset.
If you find yourself using the same combination of effects over and over use a preset.
If you find yourself writing the same expressions over and over use a preset.
If you have something cool that other After Effects users would like make a preset, and post it on Gumroad.