Tickets for season 9 and 10 tapings were not publicly available, due to the show's immense popularity. But I had a connection with the post-production technical director, who had been in touch with me for some historical information about the show. (Apparently I'm a trusted source of information!)
Myself, my wife (at the time) and some in-laws travelled 600 miles to be in Burbank for the taping. At the advice of [many], we arrived at Warner Bros. Studios plenty early for the taping, but the staff who directed us about where to go and where to stand were not good with crowd management. Every other time they moved the crowd, we ended up further and further back in line. That staff wasn't very impressive in other ways, either. For example, another show being queued for was "Everybody Loves Raymond," and the lady kept saying, "Everyone for 'Everyone for Raymond' stand over here!". So she didn't even seem to know the show name! Maybe it was her own personal joke, but she didn't seem like she was in a playful mood.
When we got to the actual sound stage for Friends, the staff there was much more professional. But apparently, as a late birthday gift for Matthew Perry, his favorite hockey team had been invited to the taping, unexpectedly taking up a lot of seats intended for other people. So we almost didn't get seated. They tried to get us to opt for a guided WB Studios tour instead, but we stuck to it and explained how far we travelled and the line problems that had occurred. Finally, they let us take some seats that had been reserved for Jennifer Aniston's guests, who hadn't shown up yet. The WB Studios staff were under a lot of pressure that day, with way too many people there, and finally were like, "Hey, if her guests can't bothered to show up at a reasonable time, that's their loss." It was already after scheduled start time, but things were running late. I don't know if those people ever did show up, but I so greatly appreciated the staff's willingness not to treat us like we didn't matter.
I found myself sitting directly behind Rosanna Arquette (movie star, sister of David Arquette, and sister-in-law to Courteney Cox-Arquette, at the time).
The cast was friendly with the audience when they were introduced, and once in a while during taping when extra fun things happened. But, of course, most of the time their focus was not on us. Paul Rudd was a big part of the episode, so we got to enjoy his presence as well.
The studio had a crowd handler / funny man with the audience, hanging out, keeping the audience engaged and laughing between scenes. Sometimes they had little contests, trivia, etc. My then-wife and I won Friends t-shirts for dancing for everyone... thoroughly embarrassing. It haunts me to this day.
Gary Halvorson (who directed many episodes) was directing that day, and (because of my weird sense of fun) I asked the crowd handler (who sometimes communicated to the cast and crew for us) to tell him that I enjoyed his work on "The Adventures of Elmo in Grouchland." Gary directed that, also. But the guy looked with at me like I was a nut and said, "I'm not going to say that." LOL.
It took MANY hours to get the show taped, on top of it starting later than scheduled. They fed us pizza at two points, I think. It was cheap, boring cheese pizza, but it kept us happy.
The girls apartment and Central Perk were used for that episode, and were easily visible. Joey and Chandlers apartment was mostly blocked off (though you could still see crew playing foosball between scenes) because that side of the stage and everything on the left of the audience area had been turned into Mike's parent's house. We couldn't directly see the scenes in that area... we had to watch it on monitors. On the right of the audience area were Ross's apartment and Richard's apartment. We couldn't see into those either... again, we watched on monitors. And scenes involving baby Emma were pre-taped and shown to us on monitors, because babies don't do well with a studio audience.
Here's a diagram of how the stage was set up that day:
They tape the show in story-order, so they were often doing one scene here, then resetting in another location. Movies are filmed out-of-order to be more efficient with their locations. But TV shows (at least ones with a studio audience) are usually presented in story-order so the audience can easily follow along. It took A LOT of time, but we were happy to experience it.
My then-wife gasped loudly when Phoebe actually ate meat in one scene, and you can hear her gasp in the background when watching that episode.
It was night and dark (maybe 8:30pm on an October night) when we left the studio. It think we had been at the Friends stage for 6-7 hours and had used another 2 hours prior to that for arrival / waiting / seating etc.