It seems nearly every program I watch has a sit spin (ahh, must be a required element, eh?). I don't think I've ever seen a "bad" sit spin -- in twenty years maybe I've seen one gal fall out of sit after catching her blade on a nick -- but then I can't say I ever gone Whoooya watching a sit spin, either. With one foot on the ice and the other out in front or "broken" what does that leave you for expressiveness?
Well, hands and arms maybe. For some reason I don't really like any movement of the hands or arms during sit: you should select and maintain a nice pose. Hands gracefully masking the face? One hand in front and one in back? Palms forward pressing? Please make them interesting somehow.
The main technical aspect of sit, what it seems to be there for, is Proof of Edge. Once you're down in position you can't modify your angular momentum with any change of body parts, so whatever rotation you bring into the sit is what you're left with. If you can keep your speed up the whole sit then you are proving you found that sweet spot on your blades with the least friction.
After checking you maintained your speed and did something unusual with your hands, I want to see your graceful struggle up from the sit. Because that of course is the other hidden facet of this element: it's not so much how you got there, but rather how you get out. Extra points if you can rise from one leg rather than bringing the other foot down to rise from two. I have enough trouble with sturdy shoes on a concrete floor standing up from a one-legged crouch; I can only imagine your effort standing with the additional mass of your skate boot. Impress me with your strong thighs and some class.