Pick the TV program you would like to review. Keep in mind that you should be an expert on the program. First, you need to actually watch the show (the first episode, first season, or whatever you are reviewing) and secondly do a little background research on the actors, director, writers, and crew. People often look for reviews when a season is first starting or when the season comes out on DVD. If you are doing a review on the first episode, release it on the day of the first show (if you already have access to the episode) or within the first week. If you are doing a review on the entire season, you'll already have access to all the episodes, which means you can release the review prior to or on the day of DVD release. Keep in mind that certain shows follow a continuous storyline, while others are generally composed of "stand-alone" shows.
Watch the first episode or entire season (depending what you are reviewing) and make notes. You need to look for a lot of different aspects of the program, so you may have to watch the episode or episodes more than once. You need to make notes on the story (writing), production value, acting, etc. If you are reviewing the entire season, highlight your favorite things about each episode as well as any negatives. If you see a common trend throughout the episodes, make note of that during the actual review.
Find your niche audience for the review. For example, if you are writing a review for a family-friendly publication, you would likely turn thumbs down on an HBO show containing violence and sex. However, if you are writing for a young adult or college audience, you would likely give the same program two thumbs up. Think about the audience you are writing for and tailor the review to that audience.
Format the TV program review appropriately. All reviews in the arts, regardless of the medium, have a common format. The review generally starts out with a brief opinion as to whether or not this show is worth the reader's time. The review then dives into the basic premise and/or plot of the episode or season, highlighting the stars of the show, the production values, and the writing. The critic then dives into what makes the program great and not so great. If you really like the program, allocate 75 percent of this section to the positives, and vice versa for a program you thought was awful. Last but not least, add a final conclusion about the show. Use a trademark acceptance (i.e. "two thumbs up") if you recommend the program.