This works with Tomcat 7 (probably works with other Tomcat versions as well)
On Windows add into catalina.bat
set CATALINA_OPTS=%CATALINA_OPTS% -Xdebug -Xrunjdwp:transport=dt_socket,server=y,suspend=n,address=8000
Then run startup.bat
And now you can connect remote debugger on port 8000