Greens should be fresh and bright, not wilted or browned.
Except for some specialty salads, greens should be in bite-size pieces.
Greens should have been properly dried before dressing and plating. Water clinging to improperly dried greens dilutes the dressing and makes the salad excessively wet.
Tossed salads should have just enough dressing to lightly coat all the greens. Dressing should not pool on the bottom of the plate.
Dressing should be appropriate to the greens. Light, delicate greens require a lighter dressing, usually a vinaigrette. Sturdier greens, such as romaine, can handle heavier dressings.