First, don't over-think it. Herbs and spices are best used to accent the natural flavor of a particular ingredient. They won't make or break your dish in the end. A quarter-teaspoon too little or too much won't be the line between wild success and horrible failure. Cooking with spices or adding herbs to a finished dish is like the artist's signature on the bottom of his painting. It's not meant to be the focal point of the creation, just the pronouncement that it's complete and ready to be enjoyed.
There is a big difference between 'seasoning' and 'flavoring'. Seasoning is the act of bringing out the natural flavors of the food with herbs and spices. Salt and pepper on a grilled chicken breast will accent the flavor of the chicken, but not change it. Flavoring is changing the flavor profile of the ingredient entirely. Chicken in a heavy cream or sherry sauce may not be immediately identifiable as chicken. The flavor, not the seasoning of the chicken is changed.
With that in mind, there are two ways to start creating your own combination of herbs and spices for a personal cooking repertoire. Either match the seasonings to the ingredient, or to a specific style of cooking or ethnicity. Use the palate-stereotypes that exist to mimic the flavors of a specific culture.
I've arranged the dry spices in my cabinet by cultural or ethnic 'teams'. These are the combinations I'll use when cooking with spices to achieve a specific international flavor. If I want to cook an Italian dish, I'll use Basil, Oregano and Garlic. Those are the flavors inherently associated with Italian Cooking.
While the cooking methods may stay exactly the same, the type of seasoning accent you place on the food can create a wide variety of everyday meals using the same ingredient. For example, sauteed pieces of chicken accented with Curry Powder, Turmeric, Cloves, and Allspice will be reminiscent of Indian Cooking. The very same sauteed chicken seasoned with Cumin, Coriander, Cilantro, and Chipotle Pepper is a Mexican dish even though the cooking methods are the same.
If you're not looking for worldwide flavors, and just want to make your everyday cooking better, there are some herbs and spices that compliment certain ingredients better than others. Combining Thyme, Tarragon, and Sage will remind you of the smell of a roasting turkey. These three seasonings are my 'Poultry Team'. I always use them to compliment chicken, turkey, duck, or quail.
Think of a beef or pork roast in the oven. Draw air through your nose deeply. What do you smell? It's probably Thyme, Rosemary, Cloves, and Black Pepper. If you can smell it in your head, you can taste it on your finished dish, and these four items should make up your 'Meats Team'. Now, create a 'Fish Team' or a 'Vegetables Team' using the herbs and spices you like best with those ingredients.
The first step to perfect seasoning is to group and associate your spices with a particular style of cooking, or to highlight the main ingredient being used. Through experimentation and tasting, you'll know what to use with a basic chicken saute, or how to season your own Asian chicken dish that you created. Aim at the ingredient or the culture for the best use of spices.
It's okay to use ethnic profiling when cooking with spices. Your goal as the cook is to use these food stereotypes to communicate the ethnic flavor profile to those enjoying the meal.
See the complete Cooking With Spices video.