Well, two things I've learned since we built our barn:
1. Drainage, drainage, drainage. Make sure your site is set up for good drainage. We've had to go back and do a lot of things to fix our drainage issues since the KY clay soil doesn't drain worth a flip. It would have been a lot easier if we had prepped the site better with some gravel or something.
2. We have a log home with a brown metal roof. We wanted to put a brown metal roof on the barn, but weren't able to get the same color without a lot of hassle. So, we ended up using plain old silver corrugated sheet metal. We're so glad that we did it that way. Our barn is probably 10 degrees cooler than it is outside in the summer because the roof reflects the sunlight so well. The brown roof would have been terribly hot!
I was normal...then I got a horse.