How to create the illusion of motion

How can you make it look like a feather/tentacle/foot/belly that kind of thing is moving. I really want to know and i would really appreciate it if someone told me.

For a still/unanimated cartoon or an animated cartoon?

Still/unanimated

An easy way is to put little curved lines around the moving object. Another way is to draw the end of the object eg feather lightly to the sides of the object, eg feather, to show where the feather/object was before.

Thanks man. You are the best

Lines of motion are a good general rule. Things which are more straightened tend to look faster while things that are curved or bent look like they're changing direction and are, therefore, slower. For tickling's sake, awkward positions which are hard to hold look like the subject is moving faster. Tomatodragon is amazing at it, and I've played around with the idea a few times. Like with this one:

<object width="450" height="380"><param name="movie" value="http://backend.deviantart.com/embed/view.swf"></param><param name="flashvars" value="id=60919328" /><param name="allowScriptAccess" value="always" /><embed src="http://backend.deviantart.com/embed/view.swf" type="application/x-shockwave-flash" width="450" flashvars="id=60919328" height="380" allowscriptaccess="always"></embed></object><br /><a href="http://www.deviantart.com/deviation/60919328/">The Tickling Fields</a> by *<a class="u" href="http://reallyreallybigbang.deviantart.com/">ReallyReallyBigBang</a> on <a href="http://www.deviantart.com">deviant</a><a href="http://www.deviantart.com">ART</a>