You play this game a few times and you begin to pick up a few traits of each of the artists. Trampier hands, for instance, have long fingers and prominent metacarpals, while DCS, well, is no Tramp.
One distinctive feature of Sutherland's work is that he often drew the far leg of people and critters in silhouette. See the troll on the left below for an idea of what I'm talking about:
Indeed, while DCS does this all the freakin' time, Tramp--the master of fine hatching--never uses this technique. Nor does--to the best of my knowledge--Tom Wham. From Baluchitherium through Yeti, if you see a leg, wing, arm, or other extremity filled in completely in black ink, it might as well have "Sutherland" written across it in flaming letters. Check out everyone's favorite pig-faced orc, below; he gets the silhouette treatment over the entire right side of his body:
But right there on the facing page of the orc you'll see Jean Wells' Otyugh illustration featuring a fully blackened rear leg as well as a mostly blackened hind tentacle.
Now I know with absolute certainty that this is a Jean Wells drawing because none of her illos appeared in the earliest printings of the MM, and the copy I had as a kid was, apparently, one of those early printings, cuz whenever I see the violet fungi or the giant rat or that bellicose otyugh I'm still taken aback by these newcomers. Fortunately for the DCS Black Leg Theory, a not-too-close inspection quickly reveals that the femur sticking out of the muck-pile is signed "Jean & Dave" so, presumably, DCS had a hand in this after all.