You probably know already, don't clip them like you would for a wether show. I'm guessing the doe you bought in your avatar was clipped just right when you bought her. Some people seem to have the natural gift for showing and then there are people like me.
You have a pinch collar, right? Get her out in the yard and set her up like you think is good and have someone take pictures. Compare the pictures to pictures of winning goats. Make adjustments and take more pictures... The biggest thing I was messing up for the first couple of years was getting that head up. If you can, you want them sort of staring at the ceiling, not looking like they are being hung while staring at a spot two feet in front of them. To accomplish this I put my hand under their muzzle and pull their head up and then slide that pinch collar all the way up their neck and hold their head in that position. Be careful about having those front and back feet *too* far in front and behind them as sometimes their top line will go to heck on you. That's where the pictures come in as it's difficult to tell when you are standing over them. Some people are good at pinching them just in front of the hip to get them to sort of squat a little which can level out that top line a little, but I have never mastered it. The people that can do it make it look ridiculously easy, so it's probably just me.