Saké is often served in those small traditional cups called ochoko. Another popular drinking vessel is a small wooden box, usually cedar, called masu. And yet the prevailing opinion, at least among most of the new saké enthusiasts, is that saké is best enjoyed when drank from a wine glass.
The ochoko is the traditional cup to enjoy sipping saké out of. When saké began to be exported from Japan, primarily to America, it was not premium daiginjo to say the least. The main product imported for years was low quality futsu-shu and restauranteurs were instructed to serve it hot to mask the inferior flavor. The small cups do not allow for the full aroma to be considered, and encourage quick consumption like the shot glasses commonly used to drink cheap tequila.
The wooden masu were originally containers for purchasing rice. But people came to use it to buy a drink of sake with in order to ensure getting the full pour they paid for. It's also fun to drink from these boxes, but they should never be used with high quality sakés, as the wood has a tendency to mask the flavors of the saké.
So wine glasses are the preferred way to drink saké, just as you would choose a glass to enjoy the aromatics of a white wine before and during drinking, so should you use a glass that allows you to enjoy the "nose" of any of the good sakés.
A couple quick comments about saké etiquette. It is customary to pour cups of saké for your friends or your guests. Pour their drinks, then allow them to pour yours. Refill their cups when empty. Pouring your own saké is considered to be bad manners.
An elder, boss or someone of higher status should allow the person of lower status to pour their drinks. There are other subtleties, as with most Japanese customs, and they are nice to learn, but remember to pour for others and you're ahead of the game.
More important is to make sure you're serving the saké at the correct temperature. Many saké manufacturers will put serving temperature information on the labels, indicating the best zones for the particular saké Otherwise there are a few rules of thumb that will help. Rule number one is never serve saké hot unless it's crap!
Namezake, or un-pasteurized sake should be stored and served cold. Similarly daiginjo and ginjo sakés are typically stored cold and should never be heated to more than room temperature. They are normally served slightly chilled.
Premium sakés like ginjo and daiginjo should be taken from refrigeration and allowed to warm up naturally as you drink them, but again never allow it to get warmer than room temperature. Try to notice at what temperature the saké tastes best to you. You may notice different flavor profiles becoming more noticeable as you hit certain temperature ranges.
It's true that some sakés are warmed in the winter in Japan, and the best temperature for a saké can vary with personal preference. On a cold day warming a nice junmai might be just the thing. Slight warming can also serve to re-vitalize a saké that's just a bit past its prime. But in general keep premium sakés chilled, and never, ever heat saké up until it's hot. Kanpai!