I've attended a few tapings, and they all have their similarities and differences.
For all of them, the plus, is that tickets are free. The downside is they usually start their line-ups several hours before show time, with lots of warning that the shows are overbooked, so you do have to prepare for long waits in cramped quarters.
Once you enter the studios, you will see what a wide angle lens can do, as all of the studios are very small, and often times kept very cold.
The shows generally have airport-style security, and it's always interesting to see how much show personel / show security is often times only feet away from the talent and guests during the taping, yet you would never know it on tv.
Another thing is, not all seats have a view. Sometimes camera, booms, and other equipment are right in your line of sight, and all you can do is look up and watch the show play out live on the monitors (a feature all shows have). While a front row seat may seem ideal, higher seats actually provide better views. I have had cameras block my view in the front rows of Late Night with Conan and Regis and Kelly.
As for the shows I've seen:
Late Night with Conan O'Brien:
The old NYC Conan show, his best years, IMO. I attended 4 tapings of Late Night from 2005-2008. After lots of waiting in the hallways of 30 Rock, you were taken up to the 6th floor, where staffers met you with free t-shirts, which were actually very nice. A dark blue with the Late Night logo embroidered on the right corner. They were nicer than the ones in the NBC store, IMO. Before show time, Brian Mccann, one of Conan's writers and bit players, would do some warm up and introduce the Max Weinberg 7. Then he would introduce Conan, who would come out, shake some hands, take a few questions, thank the audience, and choose one audience member to go on stage and receive a set of drumsticks from Max Weinberg. (note: from what I have heard, Conan no longer comes out to greet the audience on his TBS show, which is a bummer, because, IMO, that is what makes the tapings so special, some personal interaction with the host(s) and audience) During the show Conan would stay focused on the show with his producers, but once the show was over he would sing "The End of The Show Song" to the audience, thank them again, and then it was time to leave!
Taping was at 5:30pm. Lineup started around 2, where you waited for them to give you your confirmation wristband, afterwards you were free to go and return at 4:15pm in the main lobby of 30 Rock for lineup. This practice is unchanged now with Jimmy Fallon's show.
Tickets were easy to get, you just call a number which gives ticket availability and keep calling until tickets open up for the date you wish to attend. They were generally distributed about 5 weeks ahead of shows.
Late Night with Jimmy Fallon
I've seen the latest incarnation of Late Night twice in two years. It's taped right across from where Conan was, so everything from waiting in 30 Rock to the elevator ride up to the 6th floor is the same. The biggest drawback is that Jimmy has little interaction with the audience. The ticket system is identical to what Conan had. Once seated, there is a warm up comedian who does some stand up with the audience, then introduces The Roots and announcer Steve Higgins. Jimmy does not come out and greet the audience before or after the show, and during commercial breaks has his make-up girls give him touch ups or talks with producers. As the credits roll, he does come into the audience for high-fives and handshakes with those in the aisle (and during the one show, which had a cooking segment, actually brought up the food that was made and passed it down the aisles), but he doesn't actually speak with the audience or do any sort of Q&A. Many of the security staffers that monitor everything are the same guys who were there for Conan.
Late Show with David Letterman
Tickets were much harder to get for Letterman. I have been twice, once in 2009 and once in 2010, and have gotten them by submitting them through the online form, waiting until about a week before the date I selected, and receiving a phone call from the audience department asking me a trivia question (both times, what color is announcer Alan Kalter's hair). Lineup was around 1pm, we waited on the street until around 2, when we were given our confirmation passes to come back at 3:30pm for the 4:30pm taping. An intern personally hands you the tickets and tries to pep you up for the show. While it's pretty corny, supposedly if you play along with the intern and show lots of enthusiasm, you will get the lower level of seating, as it is determined by the color of return pass whether or not you are in the lower level or the balcony. Both times we were in the balcony. The first year we were in the corner, and the view sucked. The second year, we were dead center and had a good view. Eddie Brill warms up the crowd, introduces Paul Shaffer and the band, who play a few songs, and then Dave comes out about two minutes before show time, talks briefly, and allows once audience member to ask a question, and then gives a sarcastic reply. This is the only show I have been to without metal detectors. During the second year we went, a woman pulled out her camera and snapped a picture during the taping, and she was immediately removed from the theater.
During commercials, Letterman takes his jacket off, yells at staffers and his producer,sometimes wanders aimlessly around the studios, and generally seems very offputting and nasty. He doesn't seem to be at all a pleasure to be around, and several times in just two tapings we saw him rip into the staff.
Live with Regis and Kelly
I had the opportunity to see Regis and Kelly four times, and each time was a pleasure. This is, without a doubt, the most enjoyable show I have ever seen live. The ticket process is a bit archaic, you have to mail in a postcard with your requested show date, and a few weeks before show time, they will snail-mail you tickets. Not sure if this has changed in the post-Regis era, but my last taping was just this past September for Regis' farewell celebration, and it was still snail mail tickets.
As it was the only "live" show I have been to (the others are recorded in the afternoon for a night airing), the process is unchanged. The three late night shows are all recorded "live to tape", so the feel of Regis & Kelly really was no different. For a show that goes live at 9am, the audience isn't seated until almost 8:50am. At that point. executive producer Michael Gelman came out and warmed up the crowd. Regis and Kelly did not come out to greet the audience prior to the show, which is a pet peeve of mine with Jimmy Fallon, but for them it works since there is so much other time they spend with the audience. Right at 9, Gelman acts as if he is having you practice your applause one last time, but it is actually the real deal, as the theme starts and Regis and Kelly come out. During commercials, both Regis and Kelly would come out into the audience, shake hands, hold conversations, and were absolute pleasures to watch. Regis was always his usual cranky self, but that's part of his charm, and he always made time for as many audience members as possible. R&K is the only show where cameras were permitted in the studio, just no flash during the show, so both hosts posed for countless pictures, held informal Q&A's, chatted up the audience, and truly gave them a memorable experience.
Occasionally the interviews on R&K were/aren't live, so occasionally after the host chat, the interview segment(s) are previously recorded so you watch them on the monitors. The crew hang out on set, and are very friendly. After the tapings, Regis and Kelly would tape some promos for certain affiliates, do some commercial promos, and spend some more time with the crowd. When we went in June, they then pre-recorded all of the host chat segments for the July 4th dark week, so we were there until nearly noon. Another time, Morgan Freeman pre-taped his interview for a show set to air the following week. After it was all done, Regis and Kelly would say goodbye, and it was time to go. While I never got lucky, I know that when Regis had the time and/or desire, he would meet the audience in the lobby as they exited for autographs and pictures. Regis and Kelly was, without a doubt, the most audience-friendly show to attend.
So there, the four NYC shows I have attended! It's always a blast, albeit not always exactly what you expect it to be. There have been moments at Conan and Letterman where the security and show personnel almost make you feel uneasy with their presence. And it's interesting to see Letterman chew out his staff (and Conan too, to a lesser degree). After doing the four shows, Regis and Kelly truly made it fun and relaxed, encouraging you to take pictures, meet the hosts, and even wander around the set after the show, while the other three definitely have a bit of "don't look at the host directly in the eyes or you'll be bounced out of the studio" vibe to them, especially Conan and Letterman.
. Ahhhhh, the good old days. If you ever go to The Tonight Show, be prepared to stand around for a couple of hours waiting to get in the studio.