Employment Union

There are 3 unions (which in their turn are composed of several smaller unions), the christians, socialist and liberals. You can join via their websites, links to all can be found for example behind the link below. After joining the union will send you details on your monthly contributions, they usually prefer you pay via 'domiciliation'.

http://www.jobat.be/fr/articles/les-syndicats/

The unions have in general very similar programs, but there are some idealistic differences, so you need to make the comparison yourself. Sometimes it might be easiest to belong to a union which is present at your workplace. On the other hand in some companies the union politics has become internal part of the workplace power struggle and unless you want to get involved it is easier, if possible, to choose a union not present. If you are in a risk of falling unemployed it is also helpful to choose one that has an office close to where you live (you'll need to visit them to claim the unemployment benefits).

And I probably meant to say ideological, not idealistic :-)