I figured i'd start out with this question so we can all share each other's input on this!
my idea to allowing the inner child to come out in us is this:
1- Creativity. Think outside the box and not do things because everyone else is doing it. In response to why you are making something a certain way-- just say "Because I can"
2- Dance! Even if you arent comfortable doing this in public, just move around and sing and let your silly side come out when your home. Great when doing housework and great for keeping your muscles limber :-)