You will need to download and install Flex Builder, FDS and JBoss with Tomcat embedded (I am currently using 4.0.3 SP1). I assume you can figure out these installs on your own. Once you have these installed, you need to copy the following files:

[fds install]/resources/security/tomcat/flex-tomcat-common.jar
[fds install]/resources/security/tomcat/flex-tomcat-server.jar

into

[jboss root]/server/default/lib

Download the correct Xalan jars as described in "XPath Issues with JBoss 4.0.3 SP1", here http://www.adobe.com/support/documentation/en/flex/2/install.html#jboss

copy [fds install]/flex.war to a temporary directory and rename it fdsweb.war

insert into the WAR at fdsweb.war/WEB-INF/lib the Xalan jars. I have:

xalan.jar
xercesImpl.jar
xml-apis.jar

expand the war under the [jboss root]/server/default/deploy directory, calling the directory fdsweb.war

Start JBoss and go to: http://localhost:8080/fdsweb/

you should now see "Welcome to Adobe Flex Data Services 2! This is an empty .... "

In my next Coffee Break Guide, I will show you how to set up a very simple 'RPC' call between flex and java. Go drink your cold coffee !

JBoss Installation
JBoss XPath Issues
JBoss Download
Flex Data Services Download