A Comprehensive Guide to Quiche

Crisp an unsweetened pie shell under the broiler if you want to avoid a soggy crust. Layer various ingredients and bake for 45 minutes at 400 degrees. Reheat leftovers at 400 degrees; microwaving basically works but will make it sweaty and toughen the crust.

You will generally want a custardy substance in your quiche to bind the ingredients together and add more protein. Whisk together 1 egg and 1/2 cup milk, then pour that over the other ingredients.

Examples of ingredients to layer:

Cheese, but especially flavorful white cheeses, such as Swiss.
Scrambled eggs. Season with salt and pepper and keep them fairly liquidy, as they will cook further in the oven.
Fish and other seafood. Consider browning it over very high heat (does *not* need to cook at this step, the browning is solely for adding flavor and texture) before adding it to the quiche.
Spinach. Blanch it (or buy frozen spinach,) squeeze out the water, chop it up, then saute it in oil or butter. Also a good medium for your seasonings.
Onion. Dice and brown slightly.
Tomatoes. As they can be watery, don't go overboard with them.
Potato, preferably low-starch or "waxy" varieties, sliced thinly.
Olives.
Mushrooms.
Artichoke hearts.
Asparagus.
Basically, any random leftovers that could plausibly taste good together.

Suggested seasonings include garlic; most herbs, but especially tarragon, marjoram, thyme, and parsley; onion powder; nutmeg.

Example quiche:
1 layer spinach mixed with egg and milk
1 layer cheese
1 layer spinach (also with egg and milk)

Example quiche 2:
1 layer potato, mixed with grated cheese
1 layer tomato
1 layer scrambled eggs
1 layer chopped olives
1 layer potato, brushed with oil. <--This should brown in the oven, creating a tasty potatoey crust.