Things that I learned this time around...
1. Judges like lots and lots and lots of flavor and good execution. They appreciate an extra effort taken in displaying the entry and above all, they are addiment that you follow the exact instructions for entering your baked goods. eg: Don't do what I did one year by making a 3 layer cake when the instructions call for a 2 layer cake.
2. Have a good plan on how to get the cake there in one piece. Pad a box for the cake with bubble wrap, bring a tool kit for patching up any boo boos that may happen along the way and maybe have someone else drive while you hold your precious cargo.
3. Remember that your baked good may sit around for a couple of days before it is even judged. Then, it has to be on display for a few days more. Things can dry out, or worse...melt during that interim. Be prepared and choose your recipe accordingly. No 7-minute frosting, no melted chocolate ganache. Wrap your baked goods up tight when you hand them over to the staff and adjust your recipes to compensate for the delay and possible heat or humidity.
4. Practice your chosen recipes several times in the weeks leading up to the fair. There will be lots of mistakes, but that's how you will learn.
5. Have fun and above all be a good sport and take in the good words and suggestions from the judges.