First off decide what you want to see. Many sitcoms, talk shows, and games shows are filmed in Los Angeles, so you have a wide variety to choose from, and they are free so it is a great way to add an interesting and entertaining event to your vacation, not to metion the easy way to see a celebrity.
Getting tickets can be as easy as applying on the show's website or visiting a specific site that deals in these tickets. You can check the resources below. Another last minute tactic is to visit Grueman's Chinese theatre. Some shows hand out availble seats the day of the show.
Remember how to dress and act. If you are attending a talk show the better you dress the closer to the front you can be, but don't go overboard and remember with all the lights and staging it gets hot on the stage, so they keep the studios cold, so stay warm.