However, slow simmering always intensifies the flavor. Here is a simple recipe. They say good cooks are known for their sauces. Broth is the same. As you experiment with flavoring the broth, you will come up with your own special flavors.
Some people only use leeks instead of onions.
Others prefer a particular type of tomato. Broth can be delicious, on it's own. Work on it. Experiment and taste as you go. A good broth is the foundation of a great cook.