The 5.1 Adminstrator's Guide (the latest available as of April 17, 2009) falls short in places for 5.2.2.

• When downloading the stand-alone WAR, Liferay gives you a JAR file instead of a WAR. Deal with it. Instead of having to unpack the JAR manually, you can rename it by renaming the ".jar" extension to ".war" instead and putting the file in the webapps directory and letting Tomcat automatically unpack it for you upon restart. You can then shutdown Tomcat and modify the expanded application directory as needed. (Don't forget to remove the WAR file if you plan on copying the expanded contents into ROOT as prescribed by the Guide--not something I would recommend if you have other existing apps running under Tomcat.)
• The dependencies the Guide has you unzip into

  <TOMCAT_HOME>/common/lib/ext/

  are inadequate and will generate errors (NoClassDefFoundError). You will need to also copy into the directory at least the following from the EXT ZIP:

  activation.jar
  jta.jar
  mail.jar

• For catalina.bat, setting JAVA_OPTS to have

  -Xms128m -Xmx512m

  will cause PermGen space to throw OutOfMemoryError. Instead, set it to have

  -Xms128m -Xmx1024m -XX:MaxPermSize=256m

  That seems to work for me.