I agree. There is often a lot of waiting in line and waiting in the studio. Some shows are more fun to attend than others, depending on what you expect to see.
Live shows are fun because no matter what they will have to start and end on time. Many of the live shows are talent contests so you get some form of performance and the drama of the contest.
With a nighttime talk show they usually go live to tape, meaning they are not broadcasting live but they tape it as if they are. These shows run like well-oiled machines. If the show is one hour, the taping will take one hour once it begins. (Not including checking everyone in, sitting down, and the warm up guy, which can take 2 hours or more.) Sometimes there are extra bits they tape for promos or something also.
Daytime talk shows often shoot a little more casually. They can reshoot a segment or take a while between segments to change the set. These usually take longer but can get more of a film set feel this way while they change the set. (If they do).
Sitcoms take even longer and are totally different. There will be more than one take most of the time and they will want you to laugh as hard the fourth time you see it as you did the first. These are the most "Hollywood" of the experiences since it is the most behind-the-scenes, film-like experience.
Audiences Unlimited handles several scripted and other shows, the number depends on how many are in production when you want to go. Many shows resume taping in August, like Two and a Half Men.
1iota handles Jimmy Kimmel, Carson Daly and a few more. Both of those shows often have their musical guests perform a mini-concert on an outdoor stage, where they can accomodate more people than fit in the studio. If you get show tickets you will also see the mini-concert. If you get mini-concert tickets you will watch the show being taped on screens until it's time for the music. If your show does have a mini-concert, they will often play up to 5 songs, so you will see some that never air. There are often nights when a particular show has not been fully booked. If this happens at Kimmel, you can just look at his studio (next to the El Cap, across the street from the Kodak/Chinese Theatres) and there will be someone at a little desk who will give you a ticket.
If it's a busy taping season there are often people passing out free tickets in front of the Chinese. Some tickets will be for that day, some for another day.
For any show with a live audience, be prepared to be asked to clap. A lot. My hands usually are a bit sore at the end.
Try to request well in advance.
If you have minors in your party check the age limit of the show you wish to see.
Make sure everyone in your party has a photo ID. They will check.
You will go through security. Metal detectors and they will look through your purse. Some will check large bags, cameras, cellphones, some won't, some will make you take them back to your car. Don't bring anything you don't need. Don't bring anything pointy. A friend of mine had a nail file taken away once.
Most audience companies overbook 10 to 15% because of no-shows, so get there early, especially if that show/guest of the night is especially popular.
If you MUST see the Tonight Show and don't get tickets for the date you want, you can go to the studio that morning. They will pass out a handful of tickets for that night's show at 8am. There may be people camped out overnight if they really want that ticket so there may or may not be a ticket for you this way.
Some tickets are guaranteed but most are not. Make you you read the fine print.
Also in the fine print of usually a dress code. Make sure you abide by it or they can turn you away or sit you waaaay in the back.
Dress nicely, it never hurts. They will not sit someone in the front who is wearing a ratty tshirt and ripped jeans. American Idol always pulls some cute, young things from the back of the line and sits them up front.
Beware the Bus. Some audience companies actually pay people to go. If you get a large group you can attend a taping as a fundraiser. (I did this in high school) These people get priority, so if you see a bus of 20 year-olds pull into the studio, they might just have taken up 48 of the seats had you hoped to get.
I read that the minimum age for that show was 10!!!! 
