Use the following Scale values: 0% - 130% - 70% - 120% - 80% - 110% - 90% - 105% - 100% Keep the interval between the keyframes as follow: 4 - 7 - 9 - 11 -12 -13 -14 - 15 Add Motion Blur for a smoother effect Tutorial by Stefano Virgilli, Adobe Certified Instructor and Adobe Certified Expert in Adobe After Effects version 7, CS3, CS4, CS5 and CS6

Adobe After Effects (Software)EffectsAnimation (Professional Field)Tutorialvoxlabstefano virgillivideo tutorialAEMotion BlurScalePhotoshop