An opening has one job: give the audience a reason to keep listening. Do that by starting with the problem, a specific moment, a surprising fact, or a direct question. Do not open with your credentials, an apology, or housekeeping. Thirty seconds is enough, and it should contain something the audience did not already know.
Flow diagram of 4 steps: The problem, stated cold, A specific moment, A fact they will not believe, A direct question.
The first is self-introduction. "My name is X, I have worked in Y for twelve years, and today I want to talk to you about Z." Every word of that is available in the programme, and none of it answers the question the audience is actually asking, which is whether this will be worth their attention. Credentials matter, but they land far better once someone already wants to hear you.
The second is apology, usually disguised. "I am not really an expert on this", "I only had a week to prepare", "there is a lot to get through so I will move quickly". Each one tells the audience to lower their expectations, and they will oblige. If there is a genuine limitation worth stating, state it plainly once and move on.
Begin with the thing that is wrong, in one concrete sentence. "Nobody who joins this scheme is still here after six weeks." The audience now has a question they want answered, and you have their attention on loan.
One scene, thirty seconds, no preamble. A named person doing a particular thing at a particular time. Specificity is what makes people lean in; summary is what makes them relax.
Only if it is genuinely surprising and you can defend it. A statistic the audience already suspects is not an opening, it is a warm-up.
Not rhetorical. Something the audience will actually answer in their heads, and where their likely answer is wrong in an interesting way.
Slides that will be shared afterwards, when questions will be taken, how long you have — none of this needs to come first, and putting it there spends your most valuable thirty seconds on admin. Say it after the opening, or let whoever introduced you handle it.
The same applies to thanking the organisers. It is courteous and it belongs about ninety seconds in, once the audience has a reason to be glad they came.
You cannot open well until you know what the talk actually argues, and that usually changes while you draft. Writing the first line first tends to commit you to a framing you then have to defend rather than one that fits.
Delete your first three sentences and read what is left. Most openings improve, because the deleted part was throat-clearing — orienting yourself rather than the audience. If the talk now begins abruptly and well, that is your real opening.
This is the same discipline that makes titles work, and it fails for the same reason when ignored: the speaker needs the run-up, and the audience does not.
Only if the joke is about the subject and would still be worth saying without the laugh. A joke that exists to warm the room spends your opening on something unrelated to your argument, and if it does not land you have started from behind.
Around thirty seconds, or two to three sentences. Long enough to establish why this matters, short enough that you reach substance before anyone has decided the talk is not for them.
Let the opening earn the question. Establishing relevance first and identity second is almost always stronger, because credentials persuade people who are already listening and bore people who are not.