Riffing off a lovely post by the Playgoer, I wonder if anybody goes to the theater to be surprised any more. In part because I'm trying to win a race, in part because I'm an editor and a critic, and in part because I just love theater, I rarely know anything about the show I'm going to see on any given night. Have a cool poster or postcard? (Orestes 2.0) Nice; I'm game. Are you a theater company that I trust, like The Flea? (Smoke and Mirrors) Dope; I'm there. Discount offer? (Serendib) Sweet. I don't know what I'm going to get, but it hardly matters at affordable off-off and off-Broadway theaters. I admit, when I'm shelling out full-price to see Spring Awakening, I consider what I may or may not have heard about it, but even then, I don't want to know what happens in the show itself. (The gimmicked audience and needless use of meta elements on the chalkboard, ugh; everything else, anachronistic staging, yes!)
The only way my guerrilla audience tactics work is if you accept one reasonable premise: there is no such thing as bad theater. There are awful shows, but even those evoke something in you (and I actually find passable theater, or bland theater, to be far worse). And if you're at all involved in the arts, as a writer, director, amanuensis, whatever: it's a learning experience. You may see a production that gets everything wrong . . . except for one shining moment of stagecraft, and that's what lives in you and fills you. Yes, you've got to have passion for this to work; but why should we as an audience be any less receptive than we expect the actors to be? (Amendment: if you're torn between two shows, neither of which runs past the evening in question, there's nothing wrong in doing a little research; you'll feel more content with your choice, rather than restlessly wondering about the other show you're missing.)
The other advantage toward being surprised is that you lose preconceived notions. Nothing kills live theater more than stale expectation. If you've read a play before seeing it, or you've seen other productions, you should do your best to block those from your mind: we ask the actors to treat each night like it's their first, and we should do the same from our seats. I consider myself a critic, but I have very little patience for comparative analysis (and even less for those who preface their reviews with showoffy references to past productions). What's important is the immediate, visceral response (which is why blogs have such a future) -- as a person -- and what follows are the deep-seated thoughts and observations about why that work affected you as it did, or where you feel things could've been improved (in technical relation, perhaps, to other work).
I love theater. That should be enough.