I will cover some monitoring basics before getting started here. Hopefully, the three principles that I will share here are not new to you. When evaluating to monitor something, there are three base principles that you should keep in mind, they are:
Keep it simple
Keep your monitoring close to your infrastructure
Create good monitors
The first point is very easy to understand, as it is rather self-explanatory. The worst thing you could ever do is over complicate something as important as monitoring. This principle not only applies to your overall approach but it also applies to the tool with which you choose to do the monitoring. If you have to create a Visio diagram of your monitoring platform, it is too complicated.
The point of keeping your monitoring close to your infrastructure is meant to express that the tool used to monitor should physically reside close to the infrastructure/application. The monitoring platform should not have to traverse the VPNs or multiple firewalls...