When preparing to present to your local drupal group, a drupalcon, or code group, the first decision to make is to decide what you want to talk about. It is likely that anything that you would consider presenting to others is something that you are interested in and passionate about. This is good.
Start by thinking about your audience: who are they, and why would they be interested in the subject? Think of the presentation as a story with a beginning, middle and end. Picture the end of the story and then work back from there.
I recently gave a presentation to the Jacksonville Drupal group on the implementation of SASS. I was a little nervous about presenting to a group of peers on a subject I was relatively new to, so I decided to make the focus of the presentation a fast start to Sass. This allowed the technical details to be a little looser while focusing on getting Sass installed and running with a few basic tips and techniques.
So with my 'end' in mind, I went about writing the beginning and the middle. I wanted my slides to serve as a step-by-step guide to installing, configuring and using Sass from beginning to end. When I was done, my slides should allow even a person who was not at the presentation to be able to follow the steps to achieving a functioning Sass environment.
Now that I had established a framework, and a point of view for my presentation, it was time to do all the research I would need to achieve my goals. Fortunately I had recently attended several presentations on the similar subjects, so I kind of knew the flow of the talk. I also was able to identify areas that I thought could of used either more or less explanation. I read through the documentation pages for the language, as well as the supporting libraries. I felt like it was important to get a clear understanding of all of the related fields but also understand how they relate to how I was presenting the subject.
I like presentations that are informative and also have a sense of humor. However I didn't want to be writing jokes, or looking for memes. I guess a good rule is that if it fits with the subject then you can include it, but if you are in doubt I would skip it.
On slide length.
Less is more. You don't want to be just reading what is on the slide, also you don't want to overload the viewer with information. A good maxim to remember is that no speech was ever to short.
Running through the show.
To make sure that your presentation is on a track, it is a good idea to run through it several times. You can record yourself giving the presentation to hear how it sounds and flows.
Doing this will help you identify the areas in which there are obvious breaks, and also where questions might come up. Also the more comfortable you become with the material the more natural the presentation will feel.
Preparing to present
If you are using your laptop, it is a good idea to make sure that you have any connections you may need. Thunderbolt to VGA or hdmi converter are initially expensive, around $50, but if you are going to be giving presentations they will come in handy. There are also tablet /phone to VGA and hdmi connections which means you can run your presentation from a device, reducing the amount of equipment you have to carry around. This also allows you to have a backup if, for whatever reason your primary presentation method isn't working.