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In addtion to what Honeysuga said, pay very careful attention to your turnout. You want clean, conservative and well fitting in everything. You mention hunter green for his "color"; I don't know what type or level of show you're competing in, but colored saddle pads and other accessories are usually a no-no in the hunter ring. Then, pay attention to details - are you wearing a hairnet and small post or hoop earrings? All keepers tucked in? Head and feet trimmed neatly? White markings powdered? Face oiled? Hoofs painted? Boots shined? Clean, white, well fitted contour pad?
Then, you need to plan your ring strategy. In a crowded class, plan carefully so you get a few good passes in front of the judge on the long sides or the arena, especially at your best gait. Ask for a little lengthening at the walk and trot down the long side if you can do it subtly; that shows your horse at an advantage. Keep soft eyes and be looking ahead and planning ahead the entire time in a flat class to avoid getting boxed in on the rail or cut off in the corners.