How do I get better at giving talks/presenting research?
One important thing, for both casual talks and more formal talks, is your notes. Too many details and you can't use them without interrupting the flow of the talk, too little and you can get lost.

After some time, I converged to the following solution. I usually prepare one or two pages of main notes, not too densely written, with the main items I want to speak about and large signs for important things to mention at some point. Beyond two pages, I just end up caught in the moment and diverge from the planned path and improvise too much.

Usually there are some points where I could need a complicated formula, a precise statement, or a question might occur that needs one of these in order to be answered; then I simply make a mark (circled capital letters of color) where they might be needed, and write down the details along with the same mark on a second set of more detailed notes. Then I can refer to these when needed.

Another, general advice: be careful of what you do not like in other's talks, think about why, and be sure not to do that. The flaws of talks are often broadly shared, and this can only happen because we do not realize we do exactly what we blame others for.