What if you want to contribute but you don't know what? Willing to get involved surely means you are happy about the project, it means you like it and want to help around it. You can start by chatting with people on IRC (#xfce and #xfce4-dev or Freenode), that's where a lot of people start, or write reviews and blog entries, or you can take the ropes and maintain something. You can also act positive and motivate the Xfce developers crew.
Updating the FAQ is always tedious, but not when you are maintaining it. Helping on the forum from time to time can be helpful. Doing some cool screenshots and presenting them around. Or doing some attractive artwork. You can fill pages on this wiki. You can propose wish lists for this website.
There is not always something to do, but always a little at different times
Translating Xfce will give it the possibility to be accepted by more people. You don't want software that is in English, do you?
Xfce uses a Transifex platform for the translations. By registering in, you can join the translation team of your language or more and start to translate. You can meet with other people from the team and try to share the work together.
If you are new to translations everything is explained here.
The first thing to do when you are willing to contribute is to write to the developers, let them know you like their application and what you miss in it, simply give some of your thoughts. You will be surprised by the number of people never doing this! Giving feedback takes a short time and it can always be useful for both the end-users and the developers.
That was one thing, another thing is to test the application and report bugs. For writing bug reports there are some minimum steps to take into account. It must be informal, if it is a bug it must be easy to reproduce and if it is a feature request keep in mind that it must be sane not insane Testing the application after a new release is helpful, but testing the application you like from git helps the developers to fix bugs before doing a release and it might get you into knowing the code actually.
So the first place to let developers know about what you think and miss from their application is on the xfce users mailing list. It's public and every one can read and comment it, but you can also send them private messages, they all put their email addresses in the applications you use. Interesting topics will usually be asked to be put on the bug tracking system which brings us to the second place that is on Bugzilla. You need to create an account in order to create new bugs, and when you do you can select the component and the severity between “normal” and “enhancement”.
Well the obvious contribution is to write code of course! Send us patches, write your own feature and contribute it, etc. There is no big picture here. You can attach patches on Bugzilla.
If you lack an idea for a good feature to write, pick up on Bugzilla, it's full of bugs But not all of them are things to fix, some of them are enhancement propositions, check this report of Xfce core components.
If you want to get your new Xfce plugin/project hosted, or want to takeover maintainership of one of the projects lacking interest (easy to find, look in Bugzilla for pending patches not applied since a good while..), please come to the irc dev channel #xfce-dev on Freenode network. You also need to apply for a git account at our (awesome!) release manager. An Xfce developer should fulfill your request, and you should be good to go.
Our git workflow/policy is described here.