Setup a monitoring server to get alerts when hw/sw failure and wanted to define certain rules to monitor server activity. Also I wanted to get alerts when something get crashed or when sensitive files get modified. I know there are many tools in the market like nagios,nginix, netcool etc. But, I don't know how to start, I just gathered the requirements and looking for the step by step guide to begin.
I find Munin is pretty easy to use. Here is the install guide: http://guide.munin-monitoring.org/en/latest/tutorial/getting-started.html
You will find no step-by-step guide for you, every environment is different and there won't be a "Install Nagios for Kiron". But there is enough information to get you going in the copious amount of docs.