Ps

Count processes running under each user
ps -ef | awk '{print $1}' | sed '/UID/d' | sort | uniq -c | sort -nr



My thirty largest processes sorted by memory usage
ps -aux | grep teresita | sort -nr -k 4| awk '{print $1,"-",$2,"\t",$4,"%\t",$11}' | head -n30



Find the processes which are your biggest memory hogs
ps aux --sort=+\%mem | awk '{print $2,"\t",$4,"%\t",$11}'