Confession time: I actually go in blind to almost everything these days.
It's very rare for me to watch trailers, or read news updates beyond initial announcements. Once I've decided I want something, I put the blinders on completely and I won't even look at anything relating to it. Not because I'm especially spoiler averse, but because it generates very high expectations and I'm an impatient person: the more I'm looking forward to something, the more it has to live up to, and the more irritated I generally get with it. The best way to avoid this is to just go in with no expectations beyond a general feeling that I will get some enjoyment from it, and the only way to do that is to completely avoid everything related to it.
I'm actually almost always right in my initial assessment. Maybe that's because I buy the same kinds of games from the same developers so there is an inbuilt expectation of a degree of quality within that, but it's not often a game lets me down so badly I feel like I've completely wasted my time and my money, and those times I randomly decide to buy something I am often surprised by how much enjoyment I will get from it. The only real downside to this is that it can be some time before I buy something I end up really enjoying - Langrisser I & II is a great example of this, as I bought it on a whim months after release and the first game (not played the second yet) turned out to be one of the best things I've played this year!