How do I get a list of installed files from a package?

To see all the files the package installed onto your system, do this:

dpkg-query -L <package_name>

To see the files a .deb file will install

dpkg-deb -c <package_name.deb>

To see the files contained in a package NOT installed, do this once (if you haven't installed apt-file already:

sudo apt-get install apt-file
sudo apt-file update

then

apt-file list <package_name>

See this question for more

@drysdam dpkg -L <package_name> might be the best for your immediate problem, but you might like to read the Filesystem Hierarchy Standard, which describes where different types of files live in the filesystem.

It is not definitive; it is just a descriptive account of the way things "mostly" are.

More specific to Ubuntu is the Ubuntu Server Guide, which will describe everything in enough detail. (So many of the other guides gloss over too many of the details, but this should be better.)

if you just want a single installed package, you can find the package name

$ apt-cache search rabbitmq
...
librabbitmq-dev
...

then use dpkg --listfiles

$ dpkg --listfiles librabbitmq-dev
/usr/lib/x86-64/librabbit... 
. . .