What is the 'correct' location(s) to install packages/software in a Unix file system? I realize it will vary somewhat depending on the distribution you're using and the package you're installing, but I can't seem to find any tutorials that aid in deciding where it makes sense to install something.
For example, I'm currently trying to get a Ubuntu server up and running. I'm would like to install a variety of things (mysql, mercurial, ruby on rails, radiant), and I can find plenty of tutorials that say to "install in /pick/your/directory", but nothing that seems to say what the logical choice for '/pick/your/directory' would be or how to go about deciding what '/pick/your/directory' should be (if there is no universal location).