This is really something that varies show to show for me. There have been times when I saw a particular show solely because I wanted to see someone in the cast. There have been times when I went to a show because I wanted to see a production--any production--of that particular work. I will sometimes go in blind to a show because I like/trust the company who is producing it. Sometimes there will be a show that wasn't even on my radar that I'll go see if a person I trust tells me it's worth my time. More often than not, it's a combination of factors: the cast, the creative team, the plot, etc.
I read reviews regularly, but I never based my decision to see or not see something on what a particular critic has to say. The only time reading a review influences my decision to see a show is if a review brings something to my attention that I hadn't even heard of.
"You travel alone because other people are only there to remind you how much that hook hurts that we all bit down on. Wait for that one day we can bite free and get back out there in space where we belong, sail back over water, over skies, into space, the hook finally out of our mouths and we wander back out there in space spawning to other planets never to return hurrah to earth and we'll look back and can't even see these lives here anymore. Only the taste of blood to remind us we ever existed. The earth is small. We're gone. We're dead. We're safe."
-John Guare, Landscape of the Body