TV show tickets are free. Having TV tickets in your hand does not guarantee of a seat at the show (with some exceptions from iota.com). Since a lot of people make reservations and then flake out, they usually over-book. Sometimes the cast and crew happen to have a large number of guests for a particular show, and fewer seats are available for the public. Get to the taping early for the best chance of getting in.
A few shows ask you to write in or call for tickets, but most are represented by an audience company that makes tickets available online in advance. You can order your tickets and print them out at home. If you're already in LA staying at a hotel, you can also ask the concierge or front desk if they can reserve and print the tickets for you, or use the hotel's business center, if available.
For shows that haven't filled up online, you can often find "audience hunters" in front of the Chinese Theatre distributing same-day tickets.
Audiences Unlimited (www.tvtickets.com) represents a variety of sitcoms as well as the Dr. Phil Show, Funniest Home Videos and more.
www.tvtix.com has Wheel of Fortune and The Tonight Show tickets, as well as other sitcoms an talk shows.
On Camera Audiences at www.mytvtickets.com specializes in providing audiences for talent shows like American Idol, Dancing with the Stars and X Factor, game shows like The Price is Right and Let's Make a Deal, talk shows and more.
Jimmy Kimmel Live! (866) JIMMY TIX, (Call weekdays 1-4pm PST) www.1iota.com. 1iota.com also has tickets to Craig Ferguson and a variety of other daytime and nighttime talk shows and special events.
Other LA TV show tapings outside of Hollywood that may or may not be listed on the web sites above:
NBC Studios in Burbank:
Tonight Show with Jay Leno Tickets: (818) 840-3537 (also available in person the morning of the show at the NBC Studios in Burbank or at Universal Studios Hollywood ticket booth)
Ellen Tickets: www.ellentv.com or call (818) 954-5929 before noon on the day of the show to see if there are stand-by tickets.
Continue to Audience Etiquette to learn how you're expected to behave at a TV show taping.