Grab an IRC client (such as Polari or Pidgin), connect to the server irc.freenode.net and join the channel (room) #pitivi.
Do not hesitate to ask questions, and do not panic if somebody doesn't answer your question immediately. A few of our devs maintain a persistent connection to IRC even when away from the computer, and will most likely try to answer your question if you're still online, even if it may be later during the day.
If you need to speak to someone in particular, you may try mentioning the nickname (ex.: "nekohayo") if that person is online. See also the main list of people involved in the project.
Be it a bug in the software or an issue with this website, we use Phabricator to track enhancement requests and bug reports. Our bug tracker is well-organized and issues are investigated systematically. See our bug reporting info page for useful links and details.
We attend various conferences and hackfests. To know where and when you can meet us in person, follow us on Pitivi planet, on Google+, or take a look at our public calendar below: