The way I make it is very simple, and I really don't measure much - everything is to taste.
In a pot of boiling water (as much or little water as you want) I put some dashi powder - enough to make the resulting broth taste slightly fishy - about a teaspoon per quart of water or so. Then I add miso paste (I like the red, but any kind will do) - about a couple of tablespoons per quart or so until you like the flavor - add in small increments the first time so it doesn't become too strong. If it does, then just add more water. These two items form the basis of the soup into which I add whatever else I like. Dashi and miso should be available at any Asian market.
The seaweed is a specific kind - wakame, not the nori you would use in sushi. It comes dried and looks like a package of dark green weeds. Snip a couple of wakame strands directly into the simmering soup - about 1/2 inch snips is good. You'll see that the seaweed unfurls and becomes that tender yummy green stuff you see in most miso soups. You can make the wakame as small or large as you like.
As to other ingredients, I used thinly sliced boneless ribeye, firm tofu, bean sprouts, diced carrots, a diced squash, and one our baby eggplants.
First I quickly wok-fried the beef until almost done, and then removed to a bowl. Then I added the vegetables and gave them a quick fry just to give them a little flavor. The vegetables went into the pot which was simmering until they were firm but tender, then the tofu and beef were added. Finally, the pot came off the fire and I threw in a couple of chubs of glass noodles (these just need to soak in the hot soup for a few minutes off the fire - they should not be put into simmering soup or they will disintegrate.
You can always add more miso if you want more flavor.
