There are many ways to give bad talks, but one guaranteed way to make your talk worse is to add a “Thank You” slide at the end. You know the one — the big slide that says nothing but “Thank you” that you leave up after you’ve finished your talk.
Don’t do it. There’s no point. It is a complete waste of a slide. You have just spent 15, 20, 30 minutes, maybe even an hour, describing to your audience all the amazing research you have done. In fact, you have done so many amazing things that it will be hard for your audience to remember all of them, so you remind them with a conclusions slide to summarize all of your great work.
Since there will typically be at least a few minutes for questions at the end of a talk, if you leave your conclusions slide up, this has the wonderful consequence that your audience will have several minutes to stare at your conclusions slide, so that all of your results can be impressed in their memory! In fact, one of the points on your conclusions slide may even remind them of a question they had to ask you! But if you put up a “Thank you” slide at the end of your talk, that opportunity is lost. If you must, you can put a “Thank you” at the bottom of your conclusions slide. But even with that you’d really be better off without it.
That’s all I have. Thank you.