There are many ways to start a new web application in Tomcat, but this tip is for the developers who want to do so by modifying the /conf/server.xml
An easy way to do this is to write an XML file into the /webapps directory. When you restart Tomcat, server.xml updates automatically.
For example, to set up a web application in the /myweb directory, you'd add the myweb.xml file into the /webapps folder, and then edit it so it has the following content:
<Context path="/myweb" docBase="myweb" debug="0" />
Now restart Tomcat to make your new web application available.