If the bread has been baked traditionally on the stone floor of the oven, the ends should have lifted, creating a slight upwards curve. Look for the cuts, or 'tears' as they're called, to have opened giving a torn appearance to the interior. There should be an uneven texture to the crumb, as this is a sign that the dough was given a long initial rise before shaping.
Blisters on the surface of the crust are good too, and show the dough has been given a long cool second rise to increase the flavour. The crust of baguettes made with flour milled in a French style and with grain relatively low in protein should tear easily and not show any toughness. The inner crumb should be a pale cream colour, not a brilliant white, though this might not affect the flavour or the texture.
