You have a presentation scheduled in a few weeks, and therefore want to start preparing. The first step is to carefully think about the design of the talk. This does not need to take long, but is crucial. The two key slides you want to prepare are your Content slide and the Conclusion slide.
Intended for: BSc, MSc, PhD
Conclusion slide: what message do you want to bring across?
Start at the end, by building your Conclusion/Take Home Message slide. Ideally, you should be able to summarize your talk on this slide in 4-5 bullet points of a single sentence (sometimes you may need a second slide). Starting with this slide forces you to build the high-level picture of your talk.
Content slide: structure your storyline.
The second slide I always build is the Content slide, which paints the high-level storyline. Partition your story into Parts, possibly with Subsections. Indicate in the Content where your talk will have a Break (if any). Example:
i. Introduction
ii. Markov Decision Process
iii. Value function
(Break)
iv. Dynamic Programming
v. Planning versus Learning
When you move between Parts, always bring in a blank slide with only the title of the new Part in the middle. This clearly signals to the listener you will start with a new topic, and is also a perfect moment for a few seconds of silence, let everyone get back their attention.
Adjust to your audience
Maybe I should have added this on top, but always adjust your story to your audience. Are you talking to fellow experts in your field, or are these high-school students coming for a practice day at university? Try to estimate their level of prior knowledge, and adjust your material accordingly.
Adjust to you timeslot
For every talk your will be given an available timeslot (if not, then always ask the organisers, you don't want to come with 25 min of slides to find out you only have 5 min). You may for example have time for 12 min talk + 3 min questions. Then, adjust your talk accordingly! We often tend to take too many slides, because we simply can't choose, only to get a very hurried talk and an annoyed audience/moderator. Practice your talk once, and simply cut out entire sections to get within the right timeframe. It will make you much more relaxed during the talk as well.
Adjust to the required quality
This advice not only applies to presentations, but to everything: give something the preparation time it actually deserves. Is this your thesis defense or a presentation at a big conference: invest a decent amount of time! But are you presenting for 3 colleagues at an informal group discussion: keep it simple! You should never do everything at 100%, because it is simply not possible (you will burn-out very soon). Before every task (including presentations) judge how much time you roughly want to invest in it.