1. Download the liferay-portal-tomcat-5.5-5.0.1 and uncompress and inflate it into a directory.
2. cd to bin directory and issue ./startup.sh
thats it, the server stated. I was able to login to the lifray portal from a Safari browser http://localhost:8080.
Go to logs directory and tail the catalina.out and check out the logs, it should say "INFO: Server startup in 33424 ms" as an evidence that the server stated up.
Next step for me is to install a developer version of Liferay so I can start developing Portlets.