I like to start with an onion or two and a can or two of diced tomatoes .... I go from there with whatever else I have. Don't measure anything. Usually, I use a stockpot on the stove but I have been known to use a slow cooker.
I season according to what goes in the pot. If I am using potatoes I may not use the same things as when I am using rice or noodles. Some of my standard "go to" things to add, if I have them, is celery, carrots, garlic, rosemary, thyme and generous amounts of black pepper.
Generally I use beef or chicken in my soup - not as big of a fan of pork based soup even though I do like my pork on the grill or smoker.
Interesting! We've always tried to use a recipe. We are going to try our hand at just throwing things in. I use store broth but would love to get away from this. Think maybe we'll try to make chicken broth tonight.