What I do is read all the bad reviews on Gamefaq. That usually tells me what the major complaints are about the game. If none of those issues are "deal breakers" for me, I'll be much more inclined to buy it.
Although with this method, you have to watch out for popular games. They tend to attract both lovers and haters, and it's harder to get an honest review. Especially FF and Suikoden for whatever reason.