If I may add something to (2) (and (3), too) I'd say to be concise and not wander too far: keep the focus and don't waste time. Moreover I think that a contribution, let it be a comment or a main argument, is much more interesting if it's different from what it has been already said before. I often hear people asking questions or offering arguments that have shown up before, without providing any new insight. Basically you could say "Listen before you speak".
TL;DR, I offered and promised in the Post Request Thread a guide to the four highest value tips I know for doing public speaking. Here they are, with explanations below:
But there's more you can add. One friend of mine was explaining a counterintuitive study in a fairly matter of fact way, but it was a lot more enjoyable and memorable to hear about if she shared her surprise at how it turned out. A lot of the time, it's simplest to just make sure you're letting your honest reactions to what you're saying come across.
But, if you're not sure what those are, or want to explore other options, you can try dividing what you're saying into beats. (Beats is a phrase used in theatre for subdivisions within scenes. In one conversation or story, the dominant emotional tone can change, and that transition is the start of a new beat). So, try dividing up your notes or your outline into sections and just experiment with the dominant tone for the section. Here's a reworking of the emotional beats in my teaching outline:
Try looking at this list of some possible emotional tones, and see what it's like when you using them as you talk through your outline. Try reading wrong tones to a friend, to notice why they're wrong or to catch yourself if you were unnecessarily restricting your options. Sometimes tone can change a number of times in one passage (as in this marked up example), just pay attention to what prompts the shift. You can try picking a speech or a sentence that already exists, and reading it deliberately with different tones each time to get some practise and comfort using them.
So, if you work on these tips, people will be more comfortable listening to what you say (1), you'll open and close strongly (2), with a narrative arc that keeps you on track and makes your points memorable (3), and enough emotional variation to keep your audience engaged with you and your content (4). Huzzah!