We had our building site and our houseplans, only to realize that there were any number of ways to orient the house. So we had to figure out the best way to take advantage of the light and the views on our site. And since the prevailing (and often torrential) winds in our part of the Adirondacks come from the West, we had to take that into account as well.
I started by hanging out on the building site to see how the views and light patterns worked at different times of day. I scanned the surveyor's map of our building site and overlayed the floorplan of our house to see what orientation would be best. Luckily everthing worked out. Virtually every window in our house has a water view. Our front door faces North (good feng-shui, in case you're wondering), our bedrooms face East, the dining room faces West (for sunset dining) and, most importantly, our living room and screen porch face South. In the Summer, when the sun is high in the sky, the living room and porch are shaded and cool; in Winter, when the sun is low, they're filled with light all day. Also, the narrowest part of the house is pointed towards the wind, which is a good thing. So we ended up with a house that is set up to take advantage of its context at every time of the day and the year, and it's made a huge difference to the experience of living there.