I am from one of those newer teams with less than 5 comps under their belt, 4 to be exact. We went from being near dead last in our first comp to 17 overall in our last comp in Troy, would've been higher if not for a 27th in chicken.
In our first comp we garnished with green leaf lettuce and in our last comp we garnished with green leaf lettuce and appearance scores were consistent throughout, 8s & 9s with a 7 here or there.
Our biggest improvements were made by focusing on cooking the meat properly. That said one of the things we will be changing this year is the move to parsley for garnish. Just a hunch that a piece pulled from a nice putting green box has a marked advantage over a plain white box even before the food has been tasted.
Spent a lot of time observing proven winners last year and all seem to use parsley.