In professional cooking circles, it's called a broth when it starts with fresh meat, and a stock when bones yield a more gelatinous texture. If you want to wrap herbs into a bouquet garni, feel free. But if you want a lot of flavor without a lot of fuss, garlic, carrot, celery and onion do just fine. Add peppercorns if you like. Some recipes suggest using the giblets.
Many cooks skip that but do drop in the neck.
Strain it when it contains bones. Better to toss the bits, clarify your broth and cook new vegetables in it before you serve it. This is the best way to get the fat out of your soup. When you let it sit in the refrigerator overnight, all the fat rises to the top and congeals. When it's cold, you can just scrape off the yellow fat.