I usually skim the fat off my stock; I think it goes rancid after so much cooking.
Here's my basic soup, we live on it during the winter time. I start with a stock pot and saute in oil (or butter if you can) "aromatic" veggies: celery, leeks, onions, garlic--whatever you've got. When softened a bit, add in other veggies (carrots, turnips, celery root, cabbage--again, whatever's in the fridge) and stock. Cook until veggies are soft. Add cooked meat if you have any and, if you like, whatever frozen veggies you have on hand (I like peas and green beans, myself). Season to taste with salt and pepper and whatever other spices make you happy--I tend to use alot of thyme and rosemary.
If I'm really organized, I'll soak and cook some beans ahead of time and add those, too. White, garbanzo, kidney--kidney beans in chicken/turkey soup is dd's favorite.