Active Roles Server Monitoring

I am in the process of implementing a monitoring solution for all of our ARS servers and wanted to reach out to the community to get an idea and best practices on what everyone else is currently monitoring within their organization. We are currently monitoring hardware utilization CPU, RAM, and Disk space but I feel like this isn't enough. I need some advice on what exactly needs to be monitored on these ARS servers in order to assure that they are functioning properly at all times. I would like to be alerted when something goes down such as website or console or know if a certain critical service is stopped. If anyone has any ideas or would like to share what they are currently monitoring on their servers I would greatly appreciate it as this will help not only me but other businesses assure that they are being as proactive as possible. Open to any ideas or advice no matter how big or small.