Probably default knowledge to most, but I didn't find it right way. Turns out the "install" parameter, is also the "upgrade" control for a specific package.
If you're trying to update a specific package, do this:
apt-get install <package>
If the package's already installed, the latest version will be installed on top of it. Using "install" as the upgrade parameter -- who comes up with these things. :-)
Here's a useful overview of all apt-get options: apt-get package management cheat sheet.