In my last world (I'm currently running Eberron and haven't given them much thought), the gnolls were savage, but somewhat noble hunter-scavengers. They are a very political species, with various gnoll matriarchs competing with each other for prime hunting land and interesting treasures. The gnolls view non-gnolls with contempt, although they respect, to a certain degree, master hunters from other races. At least on the Western Continent, they consider flinds to be a legendary race of "super-gnolls", told in tales as their ancestors.
Oh, and they are superstitious, using a variety of fetishes and non-magical items for various ritual purposes. for this reason, those that can use visible magic, usually druids, are greatly respected and feared, and often are made matriarch (if female) or the matriarch's consort (if male).
The largest gnoll population was in the Sea of Graves, a vast undead-haunted plain scattered with tombstones, mausoleums and forgotten temples to dead gods. The gnolls ate mostly goats, birds, and carrion (some ancient graves yield disturbingly fresh bodies). They considered the ghouls, which were also common, to be rivals and occasional prey, although ghoul flesh is considered bitter and unpalatable.
Demiurge out.