While often referred to as rice wine, Saké is actually more like a beer - made from a grain - rice - which is broken down by koji mold and fermented into an alcoholic beverage. Saké shows up in Japan's first written history compiled in 712, CE. Many of us have had a ceramic cup full of hot, harsh, barely drinkable Saké in a Japanese restaurant. My introduction to the world of sake beyond the heated liquid in the ceramic cup began when Moto-I, one of America's first Sake Brew Pubs opened a mile from my house. Frequent visits there over the years always involved drinking at least one of their house Sakés. They were good and gradually built up the courage to start buying bottles.
Sake comes in grades depending how the rice is handled. The more outer rice that is polished off, the higher the grade of Saké. Daiginjo Saké has 50% or less of the rice remaining, Ginjo has 60% or less of the rice remaining, Honjozo has 70% or less of the rice remaining and Futsu-shu has no rice requirement. These grades of Saké are bottled with a little bit of distilled alcohol to bring out the aroma and smooth out the flavors. Junmai Saké does not have added alcohol and is make only with rice, water, yeast and koji. It comes in Junmai Daiginjo (50% or less of rice remaining, Junmai Ginjo (60% or less of rice remaining) and Junmai (70% or less of the rice remaining). Most Saké is pasteurized before brewing and again before shipping. Nama-zake is not and has to be refrigerated to stay fresh but can have fresher flavors. Nigori Saké is unfiltered - the hefeweizen of the Saké world and is usually milky with very small bits of rice floating around in it. My experience so far has found that anything with Junmai on the label is usually good. Anything with Daiginjo and Ginjo on the label is usually very good.
John Gauntner Sake Confidential: A Beyond-the-Basics Guide to Understanding, Tasting, Selection, and Enjoyment