(REQ) How to write a good description in 2020 ?

Hello,
I will start a project on youtube for selling some courses.
I'm a beginner on Youtube, i tried to search some informations about it ... but i found only old post.

Can you please answer this question.

How to optimize my description ?
What is the best practice for make rank a video easily ?
Do you got some template please ?

Thank you very much the community.
Have a great day.

All I can say is you should write the description as if you are explaining someone that what is your video about also don't just create a template description and use it for all your videos, also the key to rank is use low competition keywords even if they have just 50 volume searches.