The episodes of TBBT are taped in front of a live audience on Tuesday evenings. Here's a first-hand account from user Shannon on the forum of how that goes:
"I've been to 3 tapings of the show (episodes 2.22, 3.2, and 3.10) and actually going to my 4th taping next week on Tuesday ...
"When you see a taping you see the entire episode taped and they film it in order how you see it on the episode from start to finish that way us in the audience do not get confused as to the storyline. The tapings start at 6:30pm and usually last about 3 hours (yes it takes 3 hours to tape a show with less than 30 min run time haha) so we get out a little before 10pm.
"At tapings since tickets do not guarantee you will actually get in you do need to show up a couple hours early or you will not get in. Once you finally are done with the check in process they take you back in groups and you basically follow the leader around the Warner Brothers studio backlot until you get to stage 25 which is the studio the show tapes on After going through more security checks you are told where to sit (being first in line doesnt mean you get the best seats...its random how they seat you). About 30 minutes before the taping starts we watch on the tv screens above us the episode that will air before the one we watched taped (usually its the episode that they taped just last week). So in other words, we get to see 2 new episodes (one we watch on tv and the other being the one we see taped of course).
"Once we finish watching the episode on the tv's, the MC guy who "entertains" us in the audience the entire time and also directs us as to what to do in situations (like reminding us to laugh even though we've already seen the scene every time before they say "action"), will introduce the cast one by one and they basically just wave to us and then take their place either on stage or backstage if they will not be in the scene. From then on we watch the episode taped in order. We see everything except sometimes at a taping there might be 1 scene they pre-taped the day before for various reasons (its always a very short scene though...no longer than 1 min long) and we watch it on the tv screens so they can record our laughter. Throughout the taping music is constantly being played every time they yell "cut" (they actually have a DJ in the back who is playing the music) and the cast can sometimes be seen dancing to it while on stage About an hour or two into the taping the audience is given pizza and water free of charge so we don't go hungry or thirsty. Anyways during tapings very often we watch a scene anywhere from just 1 take to as many as 6 times....it various a lot but the average I'd say is 3 takes a scene. Several times the writers will have the actors try different lines just to see which line goes over the best with us and/or works simply better for the scene. When the taping is over the cast has a final curtain call one by one and all stand together on stage waving goodbye to us. The end of taping, if you go down to the rail you can try to get autographs from the cast. Every single taping is different as to how that goes though....sometimes you might not be able to get any and sometimes you can luck out and get them all to sign something (luckily that happened to me once)! FYI Kunal signs the most by far and spends a long time signing for as many people as he can. So yeah overall its a really fun thing to do and even better is thats its free haha. It's definitely a lot harder now though to get tickets....quite difficult anymore to be honest, but still possible if you are persistent enough."
"... they tape it completely in order and you see everything minus maybe 1 short clip. The last taping I went to though the short clip they pre-taped was a scene with Bernadette leaving Wolowitz on the porch there if you remember that scene in "The Gorilla Experiment." Taping was almost done and the MC told us that the writers wanted to try re-shooting that scene with us in the audience there to try some different lines so they had the actors go get dressed into their wardrobe again and they tried about 4 different lines (a different one each take). The writers are listening very carefully and constantly re-writing which is really cool to see in other words. As far as the autographs, it depends on what night you go and how the actors are feeling, but you can usually get at least 1. Jim Parsons is by far the most difficult to get a hold of though because he is of course incredibly popular and gets a bit mobbed so he tends to just go backstage right away, but I did luck out 1 time though and he stuck around long enough to sign 3 autographs including one for myself....I was very happy needless to say The cast are all really sweet because they really don't have to sign any at all. The audience unlimited staff is overall pretty cool about letting you stick around for about 10-15 minutes trying to get autographs before then you are told to leave for the night."