As in an essay, your introduction should include a "roadmap" that tells your reader what's coming.

Also as in an essay, you should signpost. These serve the same function as a topic sentence in a paragraph in an essay.

Don't make your audience work-- tell them what you want them to understand.

Roadmapping and signposting will also help you figure out whether you left something out and help you avoid needless repetition

as will...

A presentation, like an essay, needs to be well-organized to be effective.

There are many ways you can organize your presentation effectively (chronologically, thematically, etc.)

This is an example of signposting-- what am I about to tell you about?

This helps keep me as the presenter and the audience on track and following along.

It's not helpful to have too many things on one slide. If you do, it's hard for the audience to follow along, and you might forget to talk about something.

Don't add slides just to have more slides. Just as we want to avoid too much text, we want to avoid irrelevant or too-sparse slides. If you want a background slide, pick something that's relevant to your topic AND interesting to look at.

I've seen too many pixelated, side-ways, upside-down slides to count.

Review your slides. Make sure the orientation is correct and it is of high enough resolution to be usefully seen by your audience.

Another example of sign posting.

Make eye contact!

Don't bury your face in your notes, read off of your slides, or look at your shoes or off into space.

Make eye contact, but don't be awkward like these weirdos.

Don't talk too fast, which is common when you're nervous.

The audience won't be able to understand you, and you're more prone to making mistakes.

Err on the side of...

...slowing down. What sounds unnatural to you, will likely sound just right to your audience.

Of course, don't speak too slowly. It's not appropriate speak unnaturally slowly to meet the time requirement, for instance.

Don't speak too quietly. Make sure your audience can hear you. Don't turn your back on the audience or cover your mouth.

It's less common, but avoid being too loud as well. Be aware of the size and acoustics of the room. Don't shout. It's off-putting and distracting.

Be yourself. If you're a cat in a bow tie, be a cat in a bow tie.

If you're naturally funny, be funny. If you aren't, this isn't the place to ham it up.

Figure out who you are, what makes you comfortable, and what you're good at, and focus on polishing that.

Practice makes perfect. The only way to know if you have an errant slide, or how long your presentation will take you, or whether you don't actually know how to pronounce something is by practicing out loud.

Run through the whole thing. More than once.

Make sure to include a bibliography so your audience knows where your information came from.

This includes pictures.

You should also put a small citation on each picture, similarly to how you would do a parenthetical citation in the text of an essay.

Wikipedia is NOT an acceptable source. If you use Wikipedia to look something up, you must verify any fact that you use somewhere reputable (if you need help determining what's reputable, ASK ME), then cite the reputable source. If you cannot verify a fact somewhere reputable, do not use it.

Give credit where credit is due. It's not only the right thing to do, but it makes you look smart, organized, and prepared.