Your logging should show up automatically unless the jboss-log4j,xml file was changed. Double-check that file to make sure that the trace levels were not set to info or something like that. The file is in server/default/conf.
Another thought - you are talking about the log.debug("xxx") statement in your code, right? Or are you talking about logging the contents of the web service calls? If the latter, which web services framework are you using?