Server monitoring 101
I have been running a @yunohost server for ~5 years now, but there is one question I have never been able to answer: how loaded is my server? 
I know, I am a terrible sysad (actually, I am not a sysad, at all), because I have no idea how to determine:
- if my server is running smoothly
- if the server is under stress, and why
- what applications are the heaviest
- if there is the possibility of installing more apps
- when peaks of stress are happening and what is causing them
In general, I would like to understand the fundamentals of server monitoring: what are the most critical metrics and what do they mean? What parameters do I have to keep an eye on?
I installed Prometheus and Grafana, but then I realized I have absolutely no idea what to do next… Do you have any suggestions?
I thought about watching some video tutorials, but I would not really know how they would relate to YunoHost installations.
Please, if possible reply in this thread of the YunoHost forum, so that we can keep track of this useful information also for others in the future. 
Once I will have learned the basics, I would be very happy to write some pointers about this in the documentation, or an essential YunoHost Monitoring tutorial.