Best way to monitor use of memory resources for an RHEL instance

Linux and Unix-Like Red Hat
1

I wanted to know what is the best way to monitor use of memory on an RHEL server. We have 16 GB of memory for the RHEL instance but the usage at any time is more than 99%. I use /proc/meminfo on the server to check memory.

I hope, my question is clear that what is the best way to monitor use of memory on an RHEL server.

Please revert with the reply to my query.

Regards

2 
free -m
3

Thanks for your reply.