Every EU Member State maintains a national representation to the EU in Brussels in addition to their normal embassies. This is known as the "Permanent Representation" of the Member State in question, or in Eurospeak: "The Rep".
The Committee of Permanent Representatives, "COREPER", prepares much of the business dealt with at the meetings in the Council of Ministers, and it decides on 15% of the laws itself.
70% are decided upon by 275 Council working groups, which are often staffed by employees from the national representations. Only 15% are agreed upon by the Member States' ministers in the Council of Ministers itself.