The Brussels public transit system is very efficient and fairly easy to figure out. Check out www.stib.irisnet.be for the schedule and maps.
Trams, which normally travel above-ground, are numbered and are referred to by their last stop. Thus, there is 92-Fort Jaco and 92-Scharbeek. You'll need to know what number and what direction you need to take. Most areas are covered every day, but fewer trams run on Sundays and holidays, so you might need to switch between trams.
You can buy multi-day/trip passes around town or one-way tickets from the driver (1.50 euros). When you get on the tram, stamp your ticket in the orange boxes. If you need to change trams to get to your final destination, stamp it again after you board the second tram: as long as your subsequent boardings were within 60 minutes of your first, they won't count as a second trip.
Drivers don't announce stops, so you need to look out the window and follow along on the maps posted inside the tram to make sure you don't miss your stop! Also, the doors don't open unless you push the button for them. On the outside, look for a green vertical strip; inside there are blue square buttons near the doorways.
The only trick is that some tram stops have the same name but are located on different streets. For example, after departing from a north-south tram, you might need to walk around the corner to pick up an east-west tram.
Subways travel underground and are referred to in the same way as the trams: by number (1 or 2) and final destination. Note that line 1 splits at both ends, so you might need to pay attention to that.
The same tickets work in the subways and the trams, and you can switch between subways and trams as one trip. Purchase and stamp your tickets before you go to the subway platform--there are no stamping machines on the platforms or in the cars.