I'm still in production on a film about a giant frog running amuk. The overall puppet looks good but I'm selective in what I show. It's not necessarily horrific but more effective... http://www.youtube.com/watch?v=0DPgWzOW5Ks
CONTRAST!!! A lot of people have pointed out the use of dark / dim lighting, but contrast can really hide a lot of faults in your creature. Back-light the bajeebaz out of it. Back-lit dude in a mask + Jamie Lee Curtis screaming her lungs out started a franchise.
Camera shake... Easy to over-do, but POV camera shaking can be effective. If you shoot with a camera that gives you the headroom it can be easily added in post for more overall control.