Here's a quick-start guide for creating a Java servlet using Apache Tomcat with an XML configuration file:

1. Install Apache Tomcat on your local machine. You can download the latest version of Tomcat from the official website.

2. Create a new Java project in your IDE of choice.

3. Add the required Tomcat libraries to your project's classpath. These libraries are located in the lib directory of your Tomcat installation.

4. Create a new servlet class in your project:

import java.io.IOException;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

public class HelloServlet extends HttpServlet {

    protected void doGet(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        response.setContentType("text/plain");
        response.getWriter().write("Hello, World!");
    }
}

This servlet simply writes the text "Hello, World!" to the response output stream.

5. Create a new XML configuration file for your servlet. The default name for this file is web.xml and it should be located in the WEB-INF directory of your web application. Here's an example web.xml file:

<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns="http://java.sun.com/xml/ns/javaee" 
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://java.sun.com/xml/ns/javaee 
                             http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd"
         version="3.0">
         
    <servlet>
        <servlet-name>HelloServlet</servlet-name>
        <servlet-class>HelloServlet</servlet-class>
    </servlet>
    
    <servlet-mapping>
        <servlet-name>HelloServlet</servlet-name>
        <url-pattern>/hello</url-pattern>
    </servlet-mapping>
    
</web-app>

This XML file defines a new servlet named HelloServlet and maps it to the /hello URL pattern. The servlet-class element specifies the fully qualified class name of the HelloServlet class.

6. Build your project into a WAR (Web Application Archive) file. The WAR file should include your compiled servlet class and the WEB-INF directory with your web.xml file.

7. Deploy your WAR file to Tomcat. You can do this by copying the WAR file to the webapps directory of your Tomcat installation.

8. Start Tomcat by running the catalina.sh or catalina.bat script in the bin directory of your Tomcat installation.

9. Access your servlet by navigating to http://localhost:8080/your-web-app-name/hello in your web browser. You should see the text "Hello, World!" displayed in the browser window.

This quick-start guide demonstrates how to create a simple servlet using Apache Tomcat with an XML configuration file. From here, you can build on this foundation by adding more servlets, JSPs, and other web application components to your project.