It usually depends but in general I rarely read reviews before watching a film or a tv. Most reviews just share too much of plot or character details for it to be spoilery. And even opinions can colour the way I approach and see a piece of art before I've actually seen it. But I do check them out afterwards to see what others appreciated in something that I didn't, or highlight things I'd missed out on and especially to find alternative interpretations to mine because that's just fun.
When it comes to choosing, I strongly dislike Rotten Tomatoes as a metric. I have been using letterboxd.com for a few years now, where I find other, more eloquent users who share the same sensibilities as I and choose the films that get a higher rating from them. The average letterboxd rating also tends to be of better quality than Rotten Tomatoes and ImdB.
