How to check CPU Usage in the Terminal?

I like to optimize my system’s performance and like it even more if the cpu usage is at the bare minimum. To me these commands are a must for system administration and performance monitoring.

Display all CPU information

cat /proc/cpuinfo

Shows CPU usage

grep "cpu MHz" /proc/cpuinfo

Updates CPU usage every 2s

watch  grep \"cpu MHz\" /proc/cpuinfo

Watches CPU usage every 1s

watch -n 1 grep \"cpu MHz\" /proc/cpuinfo