For me, a large part is figuring out a topic. Much of what I teach is multi-day classes. Most conference presentations are about 40 minutes with maybe another 10 for questions. What topics do I love to talk about can be narrowed down to a short presentation? What do people really want to hear? What is new or not talked about enough?
So I finally come up with some ideas. Am I describing it correctly to get chosen? How do I convince the committee? Do any of them know me or is the choice from the description only? Have I specified the correct "level" for the conference notes?
And then a talk is accepted. Now I have to actually finish the presentation materials. Bullets are bad. Pictures are good. Once again, have I specified the correct level or otherwise described my presentation correctly? Will anyone attend? What if I get asked a question I cannot answer? Why does the pre-conference attendee list include [leader in field X]
This year I presented at LinuxCon and was surprised at the response. They moved rooms as the interest shown in the talk increased. I ended up with 95 people attending my "SELinux, Its about the Labels" talk. That is a lot. The keynotes hold about 900 people. The Linux Security Summit at the end of the week was in a smaller room with about 100 people. Intimidating. It went well though - at least I think it did. I had a few people come up and ask questions at the end of the talk and a few others recognize me and mention the talk later in the week. No one flamed me in person or on social media. That is a win.
I am giving the same talk again next month and I learned a few things and will be tweaking the presentation but only a small amount.