I will be making some spicy veggie soup today. What I put in it will be dependent on what I have lying about. I know that I have some carrots, parsnips and a green pepper. There may be some other vegetables. I always include a tin of chopped tomatoes - hardly any calories per tin, cheap, and tasty. I always add ginger, garlic and mixed herbs, and often some chillis and/or curry powder. I boil the veg rather than fry it and use the water as stock for the soup. The only less healthy ingredient that I use is soy sauce, which has a lot of salt/sugar in it so be sparing with that if you use it.
I use a liquidiser at the end of cooking to get a thick consistency, with just a few chunks of vegetables left to make it more interesting. Thick soup is very filling because the digestive system takes time to separate the water from the rest of the ingredients. Thin soup doesn't do the job so effectively despite having the same things in it.
That soup is for days when I am trying to keep my calorie count down. On other days I would add extras such as a tin of red kidney beans, chickpeas, or butterbeans.
I did work out the calories for a huge bowl of my soup once. The number was so small that I don't even bother thinking about it now!
Similarly, I make massive salads for low-cal days. You can eat vast quantities of salad leaves, celery, cucumber, cress, spring onions etc. because they contain very few calories. You do have to skip high-cal salad dressings though. Try some nice vinegar, lemon juice, black pepper and crushed garlic with very small additions of high-cal extras such as olive oil, honey and multigrain mustard. A tasty dressing probably has at least 3 times the calories of the salad itself so be vigilant there!
and thrice 
