Dont put your purse or bags on the table, there are superstitious beliefs about this.
Dont drink your drink while standing up at the table.
Dont talk while chewing, but if you really have to say something, put your hand in front of your mouth while talking. Dont chew with an open mouth.
Do participate in conversation while eating. Belgians usually enjoy cheerful and animated meals.
DO finish your plate, it is considered rude and a waste if you don't finish it. (be warned, Belgians tends to serve large amounts of food)
Dont show any sign of disgust if you see a Belgian dipping his/her sandwiches in their cup of coffee. Instead, try doing the same, you'll be surprised at how delicious it actually is!