There generally three different types of herring used. They are 1. Traditional marinated herring 2. Curried herring 3. Sherry Herring.
Each one has it own unique flavour . Danish herring (unless you are in Denmark ) may be purchased in speciality stores in North America. Ikea also has a selection of Scandinavian herrings.
I have never made herring and neither has my husband who is a trained professional Danish chef. As we usually only have it during the Christmas holidays we always just purchase a jar or two.
And nothing goes better with herring like a cold beer with an ice cold Aquavit (our favourite is Aalborg Jubileum) It must be kept in the freezer. Skal !