Take some shots before you right
have a few drinks. that should do it
If you are write handed try writing with your left hand or visa versa
To make it look childlike, use your non-dominant hand.
To make it shaky, clench all the muscles in your upper arm and keep them clenched as you write.
Use your off hand. Even ambidextrous people, though, have a hard time doing that. The problem is that it's almost too obvious.
just use your other hand, e.g if you're left handed use your right
Spill your cup of coffee all over it!!!!
use your other hand