5. Pay attention to your surroundings
After Leo's gone, take a look around. Is the speed limit visible? Where are you stopped in relation to the nearest intersection, and in relation to where he probably caught you? Are there any trees or bushes that could’ve blocked Leo’s view? If so, go over there and take a photo from Leo’s point of view. What cars were you around when he got you, exactly? Make, model, color, etc...
Be as specific as you can here, down to the weather, your clothing, and even what kind of cop car he’s driving. It might sound trivial, but you never know when that’ll help out.
6. Sign the citation
As Leo should tell you, this isn't an admission of guilt, merely an acknowledgement that he’s writing you a ticket, and that you’re receiving it.