More and more travellers arrive with low-cost-carriers to the Charleroi Airport a good distance outside Brussels. It is not a large airport, but it works nicely and it is a piece of cake to get to Brussels from the airport, at least if you follow our advices.
After arrival you simply pick up your luggage, walk to the outside of the terminal and look to the right. There you will find an express bus leaving from the airport the Brussels every 30th minute. The return ticket for the bus is 22 Euro and the bus will take you to the Midi Station in the center of Brussels. For your return trip you will need to get to the same place as you were dropped of as you arrived from the airport.
At the Midi Station you can jump on the metro taking you to whatever destination you would like in Brussels from there. If you want to travel on to some other destination in Belgium that can also be done from here.
If you want to be more efficient and travel with taxi instead, there are taxis waiting outside the terminal building at Charleroi Airport. To arrange with a private transfer, visit Viator.
A little advice:
Plan plenty of time for your return bus transfer to the airport. The Midi Station is enormous, so it might take some time to get from the metro to the location from where the bus leaves. When it comes to flights leaving on time, traffic delays and so on it is always useful to calculate 30 minutes more, just to be sure.