1. Add the following jvm parameters for applet:
-Xdebug -Xrunjdwp:transport=dt_socket,address=127.0.0.1:9000,suspend=y
2. In eclipse create a debug configuration.
Remote Java Application, Standard (Socket Listen), port 9000
3. The applet jar file should not be obfuscated.
4. First start listening, then start applet. The browser probably has to be restarted to reload applet.
(more detailed here: http://webmoli.com/2009/01/17/debugging-applet-code-using-eclipse/)
