Let's start with Dry Bonito, called Katsuo Ichiban-Dashi.
Boil water (600ml for 30g of Dry Bonito).
Put Dry Bonito just before it starts boiling.
Let them boil about 10 seconds.
10 seconds after, stop fire and filter them.
When you filter Katsuo Dashi, use a mesh bowl and a kitchen paper.
It could be a fabric towel.
Just let it drop naturally. Don't shake it or squeeze to drop Dashi.
That's it for Katsuo's Ichiban-Dashi.
This Katsuo's Ichiban-Dashi apply almost all Japanese food, including Miso Soup.

Next is Kelp's Dashi.
Remove all dusts on Kelp, but never wash it with water.
Put kelp into water (600ml).
Kelp makes more soup if leave them for about 30 min.
Then boil them.
Once it's boiled, then stop the heat and remove kelp.