Sometimes a handful of greens are all you need to dress up a plate. This adds color and interest to slices of quiche, sandwiches, frittatas, and other small items with minimal effort - it's incredible how much better a dish can look with just a few seconds of work.
When you're plating salad, don't just plop lettuce leaves haphazardly on a plate (or in a bowl) - this will produce flat, almost squashed-looking results. Instead, think of stacking the greens, layer by layer, so that they achieve maximum height. This will give your dish a more appetizing look.
Haphazardly plopped salad:
Stacked salad (utilizing the exactly the same leaves):
I've illustrated this point with mixed greens because that was what I had in the fridge - if you try both methods on salads with flatter leaves, you'll see an even more dramatic difference.