Of course most salads have greens but after you make that decision, you have to 'top' your salad. But too many ingredients on a salad is exactly like to many toppings on a good New York pizza; it will suck. As the saying goes: there can be too much of a good thing.
I like a lot of the basic vegetables in my salad (tomatoes, cucumbers, red onions), usually with steak or chicken for some protein. After that I usually will allow 1 or 2 odd items to add a different flavor or texture - like avocado, cranberries, mandarin oranges, pecans, pine nuts. But again, too many flavors or textures will ruin the pot.
So you have a salad. Done, right? Wrong. This is the point where everything can go horribly, horribly wrong for some people and restaurants. I personally do not like heavy dressings like ranch or blue cheese with cheese added to the salad - and if you are going to add one, the salad doesn't need to be drowning in the dressing. Heavy dressings turn the greens into something that rivals that quarter pounder and large fries in terms of health benefits and is almost as heavy. I lean towards vinaigrettes and, if I'm going to top my salad with cheese, I prefer a goat cheese or crumbled blue cheese. They work well with the vinaigrettes and I like that they stick to the lettuce and other ingredients like glue. So as you stick your fork in you are able to get lots of the ingredients at once do to the cheese acting like a glue. Shredded mozzarella and cheddar don't achieve that effect.
Lastly make sure you mix it all up before serving it. Who wants a salad with the meat and cheese on top and the dressing on the bottom with the lettuce?