Giving a good scientific talk is an art.
If you are giving a talk then try to arrange an opportunity for a trial run at a group meeting or similar.
Luckily, there are some useful resources and examples out there:
- Robert Geroch - Suggestions for Giving Talks: https://arxiv.org/pdf/gr-qc/9703019.pdf
- Jack VanderPlas - Statistics for Hackers: https://speakerdeck.com/jakevdp/statistics-for-hackers?slide=4