I had a hard time finding basic instructions, and in fact, I found that many of the more complex instructions were unnecessary. This is with Netbeans 8.1.
The XDebug package in the repositories is current and will work. You just need to set your php.ini file correctly. I found answer #1 at this link quite adequate and this is working just fine. (Exception#1: I use Chrome and did not install any extension to Firefox. Exception #2: The directory is not /etc/php5, but /etc/php/7.0, while the directory for the extensions is /etc/php/7.0/mods-available. I would imagine this last is pretty easy to figure out.)
So install php 7.0, apache2, et. al., then simply install the XDebug package and do the updates. I’m not giving my own set of instructions as I’m still not sufficiently confident.
The part that had me stalled was whether I needed to install a different XDebug version than the one in the repositories. I didn’t have to do that.