After Effects provides a variety of tools to animate characters, including Painting, Puppeting, and Parenting. Fortunately, there's an equally wide variety of tutorials available online on using these tools. Here's a survey of just some of those tutorials from Daniel Gies, Angie Taylor, Todd Kopriva, Stuart Preece, Rex Crowle, Pete McEvoy, Ryan Boyle, Marcin Zeglinkski, and Dave Scotland, plus additional tips, expressions and scripts from other After Effects and animation luminaries going all the way back to Walt Disney himself.
Ryan Boyle of Sketchy Pictures posted How to make a cartoon in After Effects, a series of 7 video tutorials that explore character design and setup, creating a walk cycle using the Puppet tool, expressions, lip sync, camera animation, and lighting in After Effects. Here's the first episode. [update: see Ryan's Crash Dummy Character Rigging Using Newton, a plug-in that does physics simulation in AE.]
Two other substantial resources also appeared not long ago: a free series on character animation in AE offered free by Daniel Gies (see embed below). and Video2brain training sets by Angie Taylor, Animated Character Design in Adobe Illustrator, 2D character animation in After Effects, and Hand drawn animation with After Effects paint tools.
Rig A Realistic Puppet, a newer 17-part series by Daniel Gies, started in October 2011. Mettle's Freeform Pro is used to add impressive depth to character in After Effects, and numerous tips are shared including IK (inverse kinematics) with the free Duik Tools (IK scripts for After Effects). Another example of 3D depth with Freeform (no longer bundled free with AE) is Gareth Jones for Virgin Media.
Gies has continued beyond his 2 big series with a variety of other tutorials, including Rocket Randee, which was later rebooted into "From Paper to After Effects," a 3rd major series showing how to build a multi-angled, segmented puppet using After Effects, Photoshop, Premiere Pro and Pro Tools. Gies continues his tutorials, for example with Using the Liquefy Effect for Head Turns and Facial Expressions.
Here's a sample from the early series by Daniel Gies and one from Duik Tools:
In Animating ‘Archer’, Dan Sarto and James Gartler speak to art director Neal Holman and animation director Bryan Fordney, who explain how Floyd County Productions use After Effects and Illustrator to create FX’s animation series Archer. Another later addition is 15 ways to improve your character animation by Antony Ward.
Todd Kopriva had been tracking and outlining character animation tutorials (including uses of the Puppet Tool), so check out his important summaries: making of "Something Left, Something Taken", tutorials for After Effects and 3D by Dave Scotland, and character animation tutorials (and more) from Robert Powers. Here's a sample from the series by Robert Powers:
Mettle sponsored a 9-part series, Build Me Some Hope: Lip-Synced Character Animation Series by David Legion. Here's the overview, but please check your audio volume:
Resources in Lip Sync in After Effects, an AE Portal roundup, may also be useful.
Covering the basics in Animate a character in After Effects at Computer Arts magazine, Stuart Preece explained how to breathe life into your character designs using After Effects' built-in tools. They also have a 2007 Animate a character in After Effects tutorial from Rex Crowle. Pete McEvoy's Rigging a character for After Effects beforehand in Illustrator also appeared that year in Digital Arts, which later added Design and Animate a Stylish 50s Cartoon Character by Ben Mounsey. Rob Mize added more in additional tutorials, for example with Character Design and Animation in AE, using shapes matched to a pencil sketch. See also more recent tutorials at AEtuts+ like Learn How to Rig and Animate a Character and Create your Own Odyssey Day 1 and Day 2 by Marcin Zeglinski.
Ross Plaskow has several intro tutorials on YouTube, starting with How To Make a Cartoon | For Beginners - After Effects and Photoshop Tutorial. And Mikey Borup posted Character Animation Fundamentals for After Effects, a 23-minute tutorial.
In Animated Cartoon Roto Shapes with mocha and After Effects, Imagineer's Mary Poplin uses mocha to create animated roto-shapes to create a simplified and stylized animated look with Cartoon and other effects in After Effects. Not quite sure what to make of it though!
Emotions and Facial Expression by Joumana Medlej is detailed and interesting, as are the many artful infographics on that website. And, LeeDanielsART has posted After Effects tutorials, including Animating 2D Cartoon Faces and Animating Coils & Antennae. Here's the latter:
There's a focus on emotion and expression in Behind the Scenes of ParaNorman: Angry Aggie, and more general interesting stuff presented with pleasant text in Making Phantom Limb by Alex Grigg (trailer below).
Tools for character animation in AE include Duik Tools, RigitScript for character rigging, as well as Puppet Tools (see above). In addition, see Animating a Walk-Cycle Using Loop Expressions by Dan Ebberts as well as his in-depth explanations of expressions in Inverse Kinematics (riffing off Brian Maffitt) and refinements in Inverse Kinematics Redux. It's important to avoid too predictable variation in motion cycles, so some may need to change up their variables more often, as when using expressions (as discussed by Anders Sundstedt) or with assistants (as mentioned in AE Preset: Back N Forth + animation aids).
Adobe posted sessions by the makers of Angry Birds from Max 2014, The Use of After Effects in the Creation of Animated Character Rigs for the Angry Birds Toons and Finessing the Art of Animation Storytelling with Creative Cloud. Impressive.
Additional resources include basic grounding found in The 12 basic principles of animation for After Effects. John Lasseter's 1987 SIGGRAPH paper based on The Illusion of Life is especially useful, even for those who find inspiration more in nature and photography. Shaun Freeman's website also provides tips and links on character animation. Vincenzo Lodigiani has a nice animated demonstration of the 12 principles of animation at Vimeo ("It's all AE.") and in pleasing Tumblr gallery:
Pan & scan techniques are useful, even though 3D camera animation is not difficult in After Effects. See Chris and Trish Meyer's article on pan & scan at Artbeats and More Motion, Less Control (on adding a human touch) at PVC for good results. For examples of taking the effect to the next level with camera mapping & multiplane animation, see another article by Trish & Chris at Artbeats, Bob Donlon's example in Son of Ken Burns, a Richard Harrington video in 'Motion Control' with After Effects. There's much more in AE Portal archive posts tagged multiplane animation, camera mapping, and the AE camera, and even more in recent books and tutorials.
Multiplane film cameras were explained well by Walt Disney in this video from 1957: