I'm not a particularly big fan of Dad's Army. It's a show hugely respect - but not one I especially find myself wanting to watch. (Hi-De-Hi was the rising show as I was growing up and getting into comedy.) But I watched the opening of the episode that was on BBC2 on Saturday (why make new comedy when you could repeat the 70s sitcom about the 40s?). Sadly it's not on iplayer, so I can't link to it. It think it's the Brain vs Brawn episode from Series 5. The first two minutes were very impressive from a writing point of view, and worth stopping to think about for a moment.
The show opens at a Rotary club. Mainwairing is there, receiving a sherry from a waitress, who says he can only have one because of rationing. Wilson arrives, who is there as Mainwairing's guest. Mainwairing points out the President of the Club and encourages Wilson to ingratiate himself with him, but Wilson turns his back to talk to the waitress, complimenting her on a pretty brooch. She is flattered and says she'll try and find him some extra sherry. Then Wilson meets the President - and it turns out he and Wilson were at school together and shared a room for a little while. Mainwairing tries to reassert supremacy by saying that Wilson works for him, but Wilson and the President walk off together, leaving Mainwairing behind - and the president says cheerio to Mainwairing, getting his name wrong. The entirety of Dad's Army is summed up beautifully in that little scene. The two main characters do their thing, and perform a mini-sketch, with nice jokes that sets up the rest of the show.
The opening of any show is, obviously, critical. I'd argue that, as the writer, you have two choices for that opening. Both are about building a relationship with your audience.
Choice One is go down this Dad's Army route, in which we re-establish the key characters leaving the audience in no doubt as to who the show is about and what the show is about. The only drawback with choice one is the sometimes it's a nice opening, and neat and clever, but not barnstormingly hilarious.
If were finding this choice a hard one, it may well be because we don't really know who the show is about, who they are in conflict with and what they are trying to achieve. We can't encapsulate the show in an opening sketch if we don't know what the show is. More work on the treatment, the characters, the outline and the stories for you, I'm afraid.
The thing to bear in mind with this choice also is that you cannot assume your audience know the characters - unless you're on Series 7 of your hit sitcom, in which case, you wouldn't be reading this blog (and if you are, can I have a job, please?) Always re-introduce your characters. Give the audience a hand getting a handle on them. This can slow things down or get in the way, which is why you could plump for:
Choice Two, which is to create a brilliant set-piece scene with a thwacking joke at the end. This might be done at the expense of re-introducing the characters to your audience, but it at least builds confident with the audience that this is going to be a funny show.
If you can pull it off, don't choose. Cheat. Do both. Miranda does this very successfully. She immediately builds rapport with the audience, establishing herself as a character, highlighting the potentially troublesome relationships in the show (with Penny, Gary, Stevie or Tilly) - and cutting to some big strong visual jokes to get the show moving comically.
If you watch the first two minutes of action (post titles) of Episode 1 of Blackadder Goes Forth (here), you learn that Blackadder is cultured (reading a book and listening to music), clever and cynical. You learn that Baldrick is very stupid, and the George is fanatically patriotic - and that Blackadder feels he's above the whole thing. That's the show. Then George produces a service revolver, and the story begins. That's how you start a show.