I usually use htop and tail -f syslog.
I am running ubuntu/nginx/memchache/php5-fcgi/varnish
closed as not constructive by EEAA, Bart De Vos, Tim Brigham, Mircea Vutcovici, Ward May 2 '12 at 4:02
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I would recommend trying each and every type of monitoring program out there. Use Google and you will find all the popular ones and as you mess with them you will know what you want and what to search for.
Make notes of how it works for you. Everyone has their own style so playing around with different systems is the only good way to find out what works for you.