Hot or Cold Sake

Are you supposed to drink sake hot or cold depending on the occasion, the meal, a preference or some combination of all those?

The bottom line is it would be your personal preference, but most sakes these days are made to be consumed cold. There are sometimes little indicators on the sake bottles to show if it should be cold, hot, or could be either...if you're interested The Sake Guy's site is a wealth of information.
http://www.sake-world.com/html/about-john.html
If you are in Tokyo when he is doing a seminar, and you are really interested in sake, it's well worth going although the venue is small so it fills up well ahead of time. He does them every month or every other month, something like that.

It depends on the type of sake you are drinking, just like the difference in how red & white wines are served & when. Sake can be served hot, room temperature or cold. It can be sweet, dry or anywhere in between. Alcohol levels vary as well. So, there is no one rule that fits. I personally like cold unfiltered sweet sake, the bottle I purchased in Shirokagawa was the best I've had.

Excellent website. The only experience I've had with sake is Gekkeikan. I'll have to see if I can find something to compare to in Kansas City.