A stock of quality can’t rely on cooked carcass and left over for flavours, it needs the strength of raw meats, the choice of meat will vary according to type of stock being made.
For a dark stock beef shin, shoulder or oxtail is recommended as these cuts contain plenty of flavour. For a lighter chicken stock, wings are great source of flavour.
These cuts also contain gelatine, which is key ingredient for many stocks as when meat cooks slowly, the collagen fibres in the connective tissue break down into gelatine.
As gelatine cools it forms a fragile solid gel.
Fish stocks are straight forward as there is no connective tissue to be broken down.
With a fish stock you are looking to capture the sweet aromatic characteristics of the vegetables and the bones. It’s best to use the bones from white fish.
Crustacean shells contain lots of fragment flavours that will reinforce the delicate aroma of shellfish stocks.
The vegetables used in a fish stock can vary but tend to be the same ones you find in a classic court bouillon.
Soups and the finishing touches of soups are what brings the dish alive. When the soup has cooled slightly you can decide what is needed, the addition of acidity can enhance the flavour especially a rich soup.
When tasting soup check if it would benefit from the addition of sherry vinegar, grated parmesan or maybe flavoured oil.
Perhaps add croutons for crunch, other ideas may be diced sauté bacon, coriander seeds. These flavours will enhance the soup but also give excitement to the palate. 
For my recipe from college of Red Cabbage Gazpacho and mustard ice cream click Week 1 stock to download it.
Food with Darcy 