How To Review Stuff

As a brief scan of this blog will reveal, I write a lot of reviews. It has now reached the stage where I can formulate a review of a TV show (or other things, but often TV) in a very short space of time. So, since it's something I have been asked for advice on, I figured the art of reviewing warrants a blog post. How do I assess stuff? Is there a technique, or do I just splurge?

And yes, some of this will be specific to reviewing TV shows, as that is my area.