First you must follow the Grands Mulets Route included in the Mont Blanc Page. Then, according to Lindsay Griffin in the book "Mont Blanc Massif. Volume I" from Alpine Club 3rd ed, page 56: cross Grand Plateau to the foot of the Corridor, a snowy vallley between the lower Rochers Rouges and Mt Maudit. Either climb the slope between the lower Rochers Rouges and a small rocky rognon (3.928 m) below (this is quicker, easier to find but more prone to avalanche and has a certain danger from serac fall), or climb between the rognon and Mt Maudit (difficult route-finding through crevassed terrain)". This approach permits you to accede to Col de la Brenva. From here follow the Mont Blanc-Maudit traverse. Difficulty: PD
According to a sign I saw posted on Aiguille du Midi, persons can set up tents pretty much any place they choose on the mountain, free of charge, provided the tents are up after sunset and down after sunrise. During the week of 10-13 September, 2002, I noted a number of tents up at "high noon," in the Col du Midi. No one seemed to care and I certainly did not see anyone out there performing official duties, fining campers, or ordering them to depart the area.