I want to enable HTTP access logging in Tomcat, what should I do?

Edit deploy/jboss-web.deployer/server.xml and uncomment the AccessLogValve valve declaration

            <!-- Access logger -->

            <Valve className="org.apache.catalina.valves.AccessLogValve"
                prefix="localhost_access_log." suffix=".log"
                pattern="common" directory="${jboss.server.home.dir}/log" 
                resolveHosts="false" />

Reference:

http://tomcat.apache.org/tomcat-6.0-doc/config/valve.html