Avoid long sentences.
Use graphs and figures well. Do not include too many or too little.
Make sure that the labels and axes of the figures explain the data well.
Be consistent with the use of tense and active/passive formation.
Write it after you have completed your work. The abstract is a summary of the whole work including the conclusions.
Do not discuss the details of your results.
Do not include references.
This part includes the main statement of your problem and the literature summary.
While writing the literature summary, do not simply list the names of the authors of papers. Read an adequate number of papers and textbooks and write a synthesis of those in your own words.
"Why did you accept my paper?", https://pubs.acs.org/doi/pdf/10.1021/jz501139d
"Good vs. bad abstracts", https://blog.webshop.elsevier.com/tips-for-writing/bad-vs-good-abstract/
"The complete guide to writing a brilliant research paper", https://www.editage.com/insights/the-complete-guide-to-writing-a-brilliant-research-paper
Steve Kirk's YouTube channel : https://www.youtube.com/channel/UCVaZKgcjl5P8zynZGJ45FFA/videos
How to read a scientific paper : https://www.sciencemag.org/careers/2016/03/how-seriously-read-scientific-paper