Miso... I think that this is the bit that has to be right from the start. The quality and type of Miso. I've been using Miso that has been too far fermented (dark coloured), and it makes the soup base too salty. I should have been using the lighter, less fermented stuff apparently! So, that is a beginning. Also, finding good noodles (Udon or Ramen) is a must. I think in the USA, there is an importer or manufacturer that is quite good, but I can't remember the name, I think they are based in Hawaii?

Here in Europe, it is pretty slim pickings... Although there are huge communities of Japanese in Paris and one of the German cities... IT might be worth it to take a short trip to stock up on the good stuff!