Find Process Id in Ubutu

Many times that I have problem with how can I stop the background process of some app like tomcat, geoserver, ruby....

Ok, I found that we can use command $ps aux | grep tomcat

the returning result is here.

1000 2957 0.0 0.0 3044 800 pts/1 S+ 10:05 0:00 grep --color=auto tomcat

so on the return result I realize that the process is of tomcat is "2957".

then I can kill it by run $sudo kill 2957