In my opinion, the key to a good salad comes down to texture and flavor. A variety of textures, like crunchy, crisp, and creamy is important along with the leafy greens. Also, a variety of flavors, like sweet, tart, bitter, savory, herby, fresh, etc. Both flavor and texture are important for an interesting and delicious salad. And, since we eat with our eyes first as they say, it's important to keep it colorful, as well.