This week's book giveaway is in the Agile and other Processes forum. We're giving away four copies of The Mikado Method and have Ola Ellnestam and Daniel Brolund on-line! See this thread for details.
I assume the servlet is running successfully in Tomcat. If so, to debug it from eclipse you need to make some changes to the tomcat start-up script along the following lines:
set JPDA_TRANSPORT=dt_socket set JPDA_ADDRESS=6666 (You can change this number if you don't like it!) catalina jpda start
Then, from eclipse create a new debug configuration for a remote Java application and specify the port as defined above.
When you run in debug mode Eclipse will connect to the VM used by Tomcat. Take a look at the Tomcat docs as they explain this better than I can here, but this should help you to get going.