After Effects On the Spot[c] Time-Saving Tips and Shortcuts from the Pros

If you spend time setting up and animating Effect properties but want to try a variation, select the Effect in the Effects Palette and Press Cmd+D (Ctrl+D) to duplicate the effect. Turn off your original Effect after pressing the Show Effect Box in the Effects Palette. Change the duplicate effect and toggle between the two to see the difference.

If it's taking a while for AE to render the effect, take a snapshot in the Composition Window and toggle between that and a duplicate effect. This is all non-destructive as you still have the original effect and keyframes.