Farm layout will largely be dictated by the shape of your property. If your property is long and narrow, you may have less options on where to put your barn and pastures than a property shaped more like a square. Smaller properties especially need to be thoughtfully designed since there is less overall room for pastures, rings and buildings. If you are able to live on the property for a while before bringing the horses home, it gives you time to know how the prevailing winds blow, how the property naturally drains and all the little nuances that will be important in your decision making process later on.
We started out with a small two stall shedrow barn and a 12 X 20 storage shed for feed, hay and tack. We located the shedrow where we thought it looked good. Unfortunately, we didn't consider drainage and the shedrow was located in a lower lying area. Be sure you locate your barn in the highest site on the property that you are able. The better the drainage, the less mud and flooding.
By the time we built the larger barn, we located it on a high point on the property. We also took into consideration ease of deliveries for hay and grain and access to the barn for the veterinarian and farrier. We took into account prevailing wind patterns, but were not able to change the location due to that. The North side of the barn does bear the brunt of the winter winds, but since we don't tend to get too much snowfall where we live, it hasn't been too much of a detriment. I like a center aisle because it is a convenient layout. If you are planning to have more than one person working out of the barn, consider putting grooming stalls off to the side. Otherwise, anyone using crossties in the center aisle is blocking access for anyone else in the barn. This not only holds true for any riders, but also the veterinarian and farrier.